Those noctua fans are a very light colour. being into some RC car modding. I can tell you that keep your rattle cans away from those fans and instead get some of this.
A good place to get it from is here
http://www.prolineskates.com/acatalog/Accessories.html
It comes in all sorts of colours. and is so easy to use a child could do it. Basically by a cheap pan for couple of quid. boil up some water. stick in a bit of salt. Then add the dye, be it the powder or the liqued. (liqued variant tends to give a slightly smoother colour) but the powder gives an excellent finish as well.
Then just stick in the fan blades and the fan casing (with the motor removed obviously) And let it soak up the dye.
The longer you leave it the darker and more vivid the colour will become.
Doing it this way instead of painting means that you are not adding anymore weight to the fans them selfs by painting them. and you are also keeping the exact same texture as the fans originaly had.
because of the light color of the noctua fans, you can get away with pretty much any colour for the surround, and just dye the darker poo brown blades black.
you can also mix the dyes to make your own custome colours.
Quick example ugly grey traxxas chassis. (ignore the carbon fibre I converted it to a mid motored car for better handeling lol)
10 miniutes in a pan and you get sexy sleek black chassis.
If you guys are interested. Tell me where I can get one of these browny yucky colour noctua fans from. And I will get one and then do a tutorial. as alot of people have these coolers, so youguys may want something to refer too. let me know.