you can find my grow journal in my signature. i am growing Afghani Bombay Kush, those are the ones showing the darker color. and yes i am using the reservoir double bucket system w drainage and like u said water probably does sit in the bottom but always is adjusted.
yesterday the room temp was 72degrees, the water temp 72degrees. ph stays steady at about 5.9 i find when able to keep the water temp down. the ppm during the entire grow has been between 700-900.. it did get up the other day due to me not accounting for superthrive but i quickly flushed so prolly only got one or two water cycles thru, showed minor signs of nute burn but got it real quick.
otherwise they've been very dark in color most of the grow, i do have 2 grand daddy purple clones in a couple buckets and they do not have the same very green color so i was just figuring it was the strain but never hurt to just make sure its not lacking or getting too much of something.
anyway, for now im going to assume its normal.. this afghani bombay kush is a strain my buddy bred and his from vague memory looked very green so maybe its common.