Pennsylvania here, ymmv.
I find Hot Pink is good all year around and my whole bag is filled with it after I figured out I really, really, really hate spending time searching discs. Bright almost-construction green is surprisingly good all year around exept in high summer when the sun is at a lower angle to really shine through grass or leaves. Out of the three primary colors, our eye perceives greens the best (probably to do with evolution in the savanna?)
I almost never bag purple or blue. I find them to be the dimmest to our eye receptors.
Construction orange is normally good but really bad in autumn/leaves. Same goes for red.
What really helps is if the disc in question glows with a UV light (365 or 395nm). What happens is the sun also emits some UV bandwidth as well and the UV discs reflect it into visible light, effectively doubling the normal visible brightness of a disc - even in barely lit forest outside. You can have the same discs, same model, and in the cheap plastic and yet it can be a coin toss if it glows. Store lights often don't help to differentiate as they contain no UV, but it's easier to tell out in the sunlight. Or take a UV flashlight and put the disc(s) in a bucket/igloo/dark and test.
Photographed are three piles of discs under UV, a mix of colors (all have some orange disc in them) and different results. Right is brightest, left side is mid-tier. Mid/Darker blues, red, or purple discs almost never light up, strangely enough yellow or white discs neither -- but that's due to the plastic formulation typically used rather than colors themselves. Some greens, pinks, orange, and baby blues do.
