HELP!

Is there anyone out there who's done a blackberry grow? I ordered seeds through visc seed company and although the plant is a beautiful lady, she's not showing any color! just mostly whites and greens, not the gorgeous purple's that the pics show when one google's or bing's "blackberry marijuana":( the plant has just started its 6th week flowering and is in a tent under 600 watts, its growing very nicely but no colors!!

night time temps are around 61-62 and days run right at 69-71, humidity is between 26-34% regularly, I'm not trying to rag on a plant that's so-far doing beautifully, but I specifically ordered blackberry for certain reasons, 1 reason was the exotic colors the strains supposed to develop! anyone know anything about this strain? thank you.