Hi DFD and well done to keep them alive this long
Trap colour, as stated, is light related, green is generally not enough light.
Dormancy - ideally below 10C but above freezing, soil damp rather than wet, dont allow them to dry out. If they do get frozen (mildly) don't worry, mine have been down to -12C before now (in a bog, not pots so the mass helps) and come through. They are tougher than some people give them credit for.
Dormancy looks different on different plants, above freezing, they keep the younger leaves, but shed the older ones (your black ones), below freezing they can lose the lot. They will stand freezing but frequent freeze/thaw cycles can kill them.
Sun is not absolutely necessary for dormancy but the light does give the plant cues as to dormancy and breaking dormancy times.
Repot in spring in sphagnum moss peat and perlite 50/50 or pure sphagnum, this causes them the least shock problems. What is your 'bog soil' made of? if it's not sphagnum it could cause problems.
Ash fall out shouldn't cause too much of a problem, water the plants from the top and empty the water tray that will flush the nutrients out of the medium.