No, not a mistake. If your cooling is adequate with one fan, then use one.
On the TRUE, the fins are close together, one fan pushing doesn't seem to have the "pressure" to do the whole job. Even with a 38mm Panaflo fan, I noticed a big difference in temps by using a "pull" fan also. ( this...
I've got an older 4 channel Rheobus, and the LED's do change color. Red is less than 1/2, blue over 1/2.
http://www.newegg.com/product/product.aspx?item=N82E16811998808
the LED's are bright.