I don't know for sure, but I would say not as much as a healthy and adequate diet. Overall though, everything plays a role, even if minute. The type of lighting also makes their colors more vibrant, such as a bulb with higher K. I use 18,000K flourescent and it is nice.
pH will not have that much of an impact as long as it is in their acceptable range (not stressing them). Since yours is 8.0, you are fine. I responded to your PM addressing your color issue.
