Regarding BVLOS, would colored strobes meet the LOS rules even though the PIC may not otherwise be able to naked eye resolve the aircraft at distance?
Yes, but within reason / common sense.
They can help you find your drone when it disappears against a background (sky or ground), but . . .
The whole VLOS thing is about knowing your drones orientation, and relate that and a response if a manned aircraft comes into the airspace around it, and could be a concern.
If a drone was say a km from the pilot, it could be that the pilot doesn't hear the aircraft soon enough, or can't see it and tell what orientation / danger their drone may be to that aircraft.
There is no hard and fast rule as everyones eyesight is different, but strobes can help you at least see your drone faster in reasonable distance circumstances.
It's well known that white leds stand out way better than green or red, or other colours.
Green / red might be handy for night time use in some case to work out what way your drone is facing, but once the drone is say approx 500m (1600') away (purely as an example), lights seems to just blur together, and colours are not terribly easy to distinguish.