On black and white non-grayscale monitors, both colors and patterns appear as patterns, thus appearing very similar. You may apply a pattern to a colored object and see little or no change in the display of the object.
This can make it difficult to use the Style Bar if you put both patterned and colored items into it. The item you're selecting in the Style Bar may be a color and not a pattern at all.
You can select the correct color or pattern by using the colors or patterns pop-up palettes.