Other people maybe be using grey-scale monitors or black and white monitors. Make sure that hotspot borders are clearly delineated if this is important to your page's use. Keep fonts clear and legible. Lucida, Times Roman, and Helvetica are particularly easy to read. Make imagemaps high-contrast.
Some web designers enjoy having blue text on a purple background in their web pages.
Even people with good vision can't read these pages. As a test, squint or put on heavy sunglasses. If your page turns into a smudge, then you need to think about how to make it more visually accessible. Believe me, good graphic design is always clear, legible, and beautiful. Some people with quadraplegic or other neurophysical impairment may use alternative pointing devices.