At the moment, the only way you can safely see colors you want across all platforms of browsers is to use any of the 216 "Web-Safe" colors. This term denotes the colors within a hexidecimal formula, which is called "RGB" for red, green and blue. The easiest way for me to remember the colors is to mix two of any of these two-number/letter combinations together:
00, 33, 66, 99, CC, FF
So, for black, you would use "#000000"; There is no RGB (red, green, blue). For a dark blue, you would use "#000033".