Same, 1/4" is enough for most products if you have to throttle it down with adjustments. If some of your runs are a lot longer than others, IMO it would be better to use 3/8" tubing and let the solenoid orifice be the restrictor.Personally I use ¼ for everything except spot free and tri foam there I use ⅜.
That's all we've ever used is black.Nylon tubing will also get brittle if it's exposed to sunlight, unless it's black. I use all black Nylon tubing now.