According to wikipedia, true cyan is an equal dose of green and blue with no red on the RGB scale. That being the case, I guess you could go with option 1. If you want a lighter shade of cyan, you could get a white LED fan as the third.
I think its safter to get 1 each first. Then look at the combination and decide whether i need another green or blue,etc. Well to answer your question why i chose cyan.... hmm well cause the only colour fans I saw sold at the stores are RGB. Well I prefer blue to green to red. So i was like wondering what does blue and green= ,which is cyan.I thought it was special and chose it.........lol