I do this as a hobby. I ano. my own parts that I make for our sleds (Snowmobiles). So from batch to batch, the color is close, but not perfect. If I am not mistaken, most R/C Aluminum parts are made from 6061 T-6. If 7075 is used, the color comes out much darker, and harder to control in a small ano. line like mine.
Most of the larger Shops must charge a minimum, that's one reason I started to do my own, not sure if I saved a whole lot, lots invested in tooling to do this!!!
There is a lot of info on the net concerning home ano. lines. Here are some links if you wanted to start your own....
http://www.caswellplating.com/
http://www.focuser.com/atm/anodize/anodize99.html
Smitty