If you've ever run into this annoying little Illustrator problem, it can be very frustrating, but it has a simple fix. Every so often you may find that no matter what color you select, Illustrator converts your selection to grayscale…
Why? Well if you open your Color palette (Window>Color), you'll most likely find that it's set to grayscale. (like below) Then the most probable reason is that you are using the wrong color scheme for this purpose. Some of the color schemes give different colors on the virtual screen and different colors on the print sheet. So, you have to select the right scheme of colors that do let the other colors interfere into. Some of the color schemes available in adobe illustrator are:
- Web Safe RGB
Grayscale scheme fades away all the colors in adobe lightroom and you do not get the true enriches colors that you can easily differentiate among them. RGB and CMYK schemes enrich the document or image with true rich colors that can really make a difference and the user gets pleased with the results. Grayscale color scheme converts all the different colors into shades of grayscale and other schemes work to change all the shades of light colors into truly rich colors. You should practice different color schemes and colors so that you can grasp more knowledge about how the different color schemes work. These color schemes become valuable when it comes to printing different illustrations on the paper.
All you have to do is set your color palette to something else, like RGB or CMYK. Now you're good to go. Personally, I have no idea why this problem has made it all the way to CS4. If I wanted to fill a shape with a gray, I'd choose a gray. This simple hack is useful for all the beginners or people who are always struggling with annoying colors and different unrecognized color schemes.
Adobe Illustrator lets you invert the pattern of colors or use any other color scheme according to your own choice.