As a general rule, the deciding factors on whether or not you can use a tool effectively are willpower and creative focus. If you're not able to still your mind and focus on a specific intent with the work, well, you're not going to have much luck...that pretty much goes without saying where magical work is concerned.
I find that colors don't really make much difference, but picking materials which are compatible with your intention is really very important where using incense for magical effect. If you're going to try to create luck, using Wormwood is probably not going to be very useful; Mugwort and Sage, however, could be plenty potent.
I like to say a quick ditty when lighting the incense too, as I find that this tends to lock the vibe I'm using into the stick in question. By doing so, I am concescrating the materia magica and then setting it alight such that the spirits I employ may do the deed I ask of them.
Its a simple methodology, but one worth remembering.