Dyes and cordination
Dragonsworn’s Dyealogue shows what each dye color looks like on cloth, leather and metal when you mouseover a color:
http://www.dragonsworn.net/dyes/
Color Scheme Designer 3 shows which colors are complementary when using a pair of colors, or three, or four:
http://colorschemedesigner.com/
Using the two together, you might be able to find some good dye combinations.
I can add that certain areas will dye differently, even on the same armor set – and you may need to use different dyes to achieve a uniform look. Eg. on my main character I have the vigil medium chest dyed blue shade, the vigil gloves are died iron and they look an identical shade in-game.
You can find complimentary shades with the Dyealogue (first link from Guppy), then it’s very cheap to buy named dyes on the TP unless you’re after something that everyone wants like black or white.
Colour combinations are of course a matter of taste, but I ended up very satisfied with a theme based around a combination of blue shade/mushroom/tarnished steel.