I've used three wall o waters since 2008. In 2008 my notes say the night temps were in the 40 F range. I planted outside a sickly looking Purple Pruden tom on 4-12-08 and put a red wall o water around it but by 4-18 it was taller and bushier than the other Purple Priudens. This is hardly a scientific study though. I still only own three wall o waters and won't spend the money for more.
On super cold nights I'd cover them with plastic or fleece.
What the university study on red plastic showed was the red light waves boost a plant hormone. I've used red plastic mulch under most of the tom plant beds and do seem to get a good harvest though haven't kept good enough measurements to prove that.
Some problems in making a scientific study are: I plant many different varieties, germinating them on different schedules, transplanting out on different days, planting them in different light and moisture situations, feeding them different days and not weighing all the produce, and some get attacked by tomato horn worms and blight.
