Neither blue nor clear will let in much UV at all. The polymer material used to make the covers is basically a UV stabilized polyethylene. The UV stabilizers absorbs the UV strongly in order to protect the PE from degradation. So either cover will work and block most of the UV.
The covers themselves don't capture much heat. Their primary benefit comes from the fact that they stop evaporation of the water from the pool which is a huge source of heat loss because the latent heat of vaporization is very large for water and so when water evaporates it takes a huge amount of heat energy away with it.
I found that when I used my bubble cover last year, my pH rise all but stopped (no CO2 outgassing) and I was able to turn my SWG all the way down to 15% and still maintain adequate FC. I also built one of those DIY Solar Rollers. The problems I ran into are these -
1. My pool is free form with a lot of curves and it is roughly 18' X 38'. So even with the cover split in two, it was a major PITA to take on and off the pool. Each roller was over 18' long and even with an 8mil cover, they weighed a ton due to water retention. They were very unwieldy and required 2 people to take off and put on.
2. I live in the desert with day time temps well over 100F from mid-May through July. You simply can not leave a pool covered during the day or else the water temperature will hit 100F in no time. Hot water will have a much larger FC demand and will just be uncomfortable to swim in. Because of point #1 above, the cover basically was left off all summer long which negated any chemistry benefit.
Because you live in Massachusetts, I believe a cover will help you a lot and your pool is basically rectangular which means you'll have a much easier time cutting the cover up into more manageable sections. Just be advised that they do weigh a lot when they are saturated with water so you might need an extra set of hands to help out.
