John
The desktop icons are different simply because they are usually displayed in
front of a picture or solid background color, that some users change often.
Because of this, the text on these icons is programmed to be either white
(for dark backgrounds) or black (for light backgrounds). But there is a fine
line between deciding when the text should change from white to black. This
usually works OK, but some backgrounds that have a great variety of colors
can be difficult. This is what the drop shadows option was designed to help
overcome, especially when the icon text is white.
The ability to color the fonts simply would not work, because you would end
up with some text visible and some text not visible, depending on the colors
of the background.
You can see this effect and the extent of the problem by going to
Personalize/Desktop Backgrounds and selecting Soild Colors. With the desktop
visible, select the light/dark colors and then the different shades of the
colors.