Color theorists and designers in fashion or computer graphics have coined phrases based around what colors shouldn't go together. A recent forum post, Red and Green Should Not Be Seen? discusses two of the sayings ("Red and Green Should Not Be Seen" and "Blue and Green Should Never Be Seen Without Something in Between"), and some lovers have even responded in protest, showing how there is no 'wrong' in love. Here are some palettes and applications of the forbidden colors that really work.
Red and Green Seen
Blue and Green Seen
Oddly, these color rules work under specific contexts, which follow 'clashing' colors. Sure, red flowers on green leaves make perfect sense, and can be beautiful, but red text on a green background doesn't always work, so there is some weight to the statements. Of course, that weight really shouldn't be the end-all. Other color combinations that are said to not work are as follows:
Pink and Mauve
Pink and Orange
Brown and Black
What I've found to be true about what's "right" and "wrong" is that a good general rule, opposed to gospel. Because colors are flexible, it follows that these rules don't always apply. What it really seems to come down to is using colors correctly. Using colors that 'clash' properly can give a wonderful contrast. In the world of color, I've found that there's no such thing as 'no' in the world of color.