Certified GKH Gardening Expert
I find that exposing mycelium to some light helps it to colonize faster, in spite of old knowledge that says otherwise!
I have colonized species over several genera, both, in darkness and in fruiting conditions. What I have found is that most will perform the same or better, in the light, as long as your moisture is on point.
The exception is with Agaricus bisporus...
If you want that pristine, white, button- Those bad boys need to be grown in darkness. Otherwise, you will see quite a bit of brown coloration.