I've always mixed my tubes colouration for two reasons. To give a bright pleasant effect to my tanks and to edge my bets.

My new PC lighting consists of 2 double tubes:-
Freshwater Tropical : White 7100k + Pink 8000k
Freshwater Plant : Pink 8000k + Blue 12000k

The k rating looked high to me but my plants have given it the thumbs (or is that leaves?) up. Colouration is also good to me.

Ian