Take for instance your current sig. You have a complementary color scheme right now. Yellow and Purple are opposite of each other on the color wheel. If I were you, I would take a look at some basic color theory. Look up color schemes such as split complementary, analogous, monochromatic, etc. See what they have to offer.
Color is very powerful. Changing the colors of any sig can drastically change the feel of the piece. I like using an analogous color scheme in my work that includes the range from orange to a brownish yellow. (Analogous being a few colors all close to each other on the color wheel) This creates a "fall" type of feeling, or possibly a somber feeling if you will. Colors represent feelings, they aren't just the color of something. If you make a piece that is green, yellow, and maybe a white, you have a springish type feel. Spring = rebirth, new life, growth.
If you need a good website (done in flash, and awesome) that can tell you about color, try:
http://www.mariaclaudiacortes.comCheck it out!

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Theseus - 3x