What Wicked said was true for me as well.
I started with 2 blue +, one GE 6500, one aquablue. This was way too white so I swapped the 6500 for a purple +. That was better, but the purple is a lot of purple if your only light source is the 4-bulb T5. With a 6 bulb, or when I added 42 LED's to the setup, the purple looked good, but with 4-bulb I would do 3 blue + and an aquablue.