Thank you!
Your question is a good one, and unfortunately or not (depends how much you like to read my ramblings..lol) the answer may not be just a quick one unless I just leave it as;
Answer: I am not sure, but I'd imagine difficult to see in bright sunlight.
Answer reasoning for fun, but honestly:
1.) I haven't had these guns more than a couple months, and have been working on/playing with them only, not having actually shot them or aimed them in the outdoor sun.
2.) Other than these last few days, the weather where I live in MN is cloudy (rainy) and dreary 5 of 7 days a week, and the the remaining 2 usually partly cloudy anyway.
3.) I have a difficult time (now with older eyes) with any smaller/rudimentary sight pictures like this even black/blue so I've learned to use no sights (7-10 years speaking) or more appropriately the (fuzzy) sight picture combined with point shooting much of the time. Out to 25 yards I can really squint to see the sight picture, but it's tedious at best.
That was probably more info than you were looking for...