I could go into great explanation on color effects but why bother when a guru has already done it for us. Below is an article by Dr George Fix that says it all....

Article by Dr. George Fix

    Color affects the appreciation and evaluation of beer in subtle but definite ways. The "halo effect" refer to a situation where a positive (or negative) response to one attribute leads to an over evaluation (or under evaluation) of other attributes. The color of beer can be a powerful but often subconscious generator of the "halo effect."

    An example is the low marks given to otherwise satisfactory beers in competitions where the entry's color is inappropriate for the category. In professional tasting, the "halo effect" is generally regarded as an unacceptable bias. However, in less formal settings it reflects the natural influence that physical appearance of a food or beverage has over sensory anticipation. For this, and other reasons, color control in brewing is important, and the goal of this chapter is to review the basic issues. Before describing the test we first review the units in which beer and wort color are measured, and then review the factors that affect color in malting and brewing.

COLOR UNITS
    Beer and wort color traditionally have been measured visually, and early on the Lovibond (degL) scale was adopted as a standard. This consists of a well-defined set of color samples that are used for comparison. A visual match with a beer or wort sample defines the degL of the sample. In modern brewing, photometric methods have replaced visual comparison, and the American Society of Brewing Chemists has developed the so-called Standard Reference Method (SRM), which is widely used. Results are expressed as degrees SRM, and for the purposes of this article these units can be regarded as the same as degL. Some examples are presented in the chart below.

Standard Reference Method (SRM) for Beer Color Evaluation

(See table 1 above)

    It is important to know that totally different units are used in England and Europe (i.e., degrees EBC). This is because of the different analytical procedures that are used for measurement. The following formulas have been used to relate these units:

(degEBC) = 2.65 x (degL) - 1.2

(degL) = 0.377 x (degEBC) + 0.45

    I have found that they give reasonable results for light-colored beers (e.g., those whose color does not exceed 4 degL); however, they are inaccurate for deeper-colored beers. Discussions with Roger Briess of Briess Malting Company indicate that these formulas are not held in high regard by professionals.

INFLUENCE OF MALT
    After the grain is steeped with water, it is allowed to germinate, then is dried in the kiln. It is in the kiln where coloring pigments such as melanoidins in malt are formed via the Maillard or browning reaction, a very common oxidation that occurs in many foods when they are cooked or exposed to air. By controlling the kiln temperature, the maltster can control the color of the kernels and hence their coloring potential in brewing. Typical values for various malt types are shown in Table 2.

    A rule sometimes used by homebrewers is that the color contributed by a malt is equal to its concentration in pounds per gallon times its color rating in degL. For pale beers this rule can give reasonable results. For example, 10 pounds of pale malt with color 1.6 degL in five gallons should produce a beer whose color is near

1.6 x 10/5 = 3.2degL.

    But for darker colored beers this rule can give erratic results. It also ignores the factors other than malt that contribute to beer color. Cereal adjuncts like rice make no contribution to beer color. Corn and unmalted barley have only a slight effect.

(See table 2 above)

INFLUENCE OF BREWING CONDITIONS
    Differences in brewing conditions can lead to substantial color changes in the finished beer, these effects being particularly important for beers at 5 degL or less.

    Water As the alkalinity of the water increases, so does the extraction rate of the coloring pigments in malt. The mash pH I has the same effect, and increasing pH leads to worts with deeper color.

    Mash Color increases with the amount of contact time with the grains. Thus, a prolonged mash will produce a deeper-colored beer than a short mash.

    Kettle boil The Maillard reaction also takes place as wort is boiled; therefore, wort color increases with boil time. A fact that is sometimes overlooked is that wort simmering has the same effect. The point is that this will lead to an incomplete hot and cold break, which in turn leaves more coloring elements in the finished wort.

    Hops Some color is obtained from hops both in the kettle and in storage containers when postfermentation hopping is used.

    Fermentation The proteinous matter produced during the cold break is full of coloring materials and, hence, removal of these materials will reduce color. It has been reported that color changes during fermentation vary with yeast strain.

    Filtration This can dramatically reduce color. It should be noted that a clear beer will appear to be lighter color than turbid beer.

    Oxidation

    At all stages of brewing, air pickup will deepen beer color. This is as true of hot wort production as it is of bottled beer with head-space air.

BRIESS COLOR TEST
    This is a simple test designed for homebrewers and microbrewers. Comparisons have shown that will give color readings with errors more than on percent for beer whose color is 17 degL or less. Beer whose color exceeds 17 degL will be essentially black in appearance. It is not particularly important to quantify color beyond this point. The standard for this test is Michelob Classic Dark. The reason is that it is widely available, and its color is known (17 degL). On very rare occasions one will come across old bottles of this beer where haze has developed because of mishandling by distributors. These should not be used in this test. By the same token, the sample to be tested should clear and free of haze. The test consists of diluting the standard with water until a color match with the sample is obtained. Figure 2 gives the relationship between the amount of water added and the degL of the sample.

This is an approximate Graph Plot. Points to plot your own accurate plot will be provided if interest is shown.

MATERIALS NEEDED

1. Distilled water--Colored tap water can increase the errors in this test from I percent to 10 or 20 percent.
2. Blender--Dissolved CO2 in the beer will affect its color. Both the standard and the sample should be degassed. This can be done in a blender. A lot of foam will be created, but once it recedes and the beer falls clear it is ready for testing.
3. Light source--It is important for the visual comparison to take place in a well-lighted environment. Ideally, this consists of a lamp with a 100watt bulb against a white background. Be sure to use the reflected rather than direct light, and place the samples the same distance from the light source Also, take time in making the comparison because the difference in one or two degL is not that great.
4. Vessels--These are the most important components to this test. After extensive experimentation it became clear that two sets are needed. For detailed testing, two glass jars of one-inch diameter and a capacity of at least 125 milliliters are best. For samples below 10 degL the volume of these vessels is not large enough. Two white 12-ounce export (long neck returnable bottles will be needed. The Miller Brewin Co. has been using these bottles. So has Corona, but the label, which cannot be removed, is a distraction.
5. Syringe--This is needed to measure 10 cc = 10 ml of water.

PROCEDURE

1. Clean everything.
2. De-gas standard and then sample in blender.
3. Measure in 20 ml of standard beer in export bottle No. 1.
4. Measure in 20 ml of sample beer in export bottle No. 2.
5. If colors are different, measure in 10 ml of distilled water to bottle No. 1 and 10 ml of sample beer to export bottle No. 2.
6. Continue Step 5 until colors become close. At this point the comparisons should be made in the one-inch diameter jars. Transfer 25 to 50 ml into these from the export bottles and return after comparison. Cut the water and sample beer increment from 10 ml to 5 ml.
7. When a color match is obtained, record the total amount of water added. Figure 2 gives the associated degL.

EXAMPLE - BASS PALE ALE
    At the start the 20 ml of standard beer (Michelob Classic Dark) will be discernibly darker than the sample (Bass). After adding 30 ml of water to the standard, the colors will become close, and at this point the one-inch jars are needed. A match is obtained after an additional 10 ml of water is added. Thus a total of 40 ml of water was needed, and from Figure 2, we see that Bass has a color of 10 degL. Since only 60 ml of liquid was used in each bottle, the entire test could have done in the one-inch diameter jars.

    Note that the relationship between degL and dilution water is not linear. For example, adding 20 ml of water to 20 ml of Michelob Classic Dark (17 degL) will not cut the color in half. In fact, instead of 17/2 = 8.5 degL the color will be higher, namely 13 degL (see Figure 2). This lack of proportionality is why the relationship between degL and degrees EBC can be in error. It also explains why beer color and malt color are not proportional.

    At the lower color range, on the other hand, proportionality is approximately valid. Thus, diluting 20 ml of Molson Export Ale (4 degL) with 20 ml of water will give a color very close to Budweiser (2degL). More generally for beers whose color is 4 degL or less, the curve in Figure 2 is given by

    degL = 4(140/VA + 20) where VA is the dilution water in ml.

    (The author acknowledges the significant contributions made through conversations with Roger Briess. In fact, the simple color test described above is essentially his idea. The author's contribution was to work out the data represented in Figure 2.)