I believe yellow/orange/red are least likely to attract bugs, but green/blue/UV will. Bug lights are typically yellow. I like green as a nightlight colour but have not tried to read under it...suspect it may cause some eyestrain eventually.
You could try yellow or amber filter over white LED flashlight. Pure yellow/amber lights don't seem very common.
The other thing about reading from a flashlight, you probably want something more "floody" than a spot beam which might be a bit bright on the page, likely not uniform, and could have some annoying artifacts such as fringing. A small COB light with filter might do the trick.