Hey what key is Blue on Black by Kenny Wayne Sheppard? The chords are D, C,G with an A mixed in everyone in a while. Also what scale is the solo in? Thanks
I would call this your basic I bVII IV progression. So key of D. Solo from what I recall is D minor pentatonic.

Other songs using this same progression: Back in Black, Good Times Bad Times verse, Gloria, Panama, Sweet Home Alabama.

Which leads to my next point (if you know the story behind Sweet Home Alabama) , that inevitably you will find some people who say its not a I bVII IV progression but instead is a V IV I progression. So you may find some people who would say Blue on Black is in key of G instead of D.

Which never made much sense to me, because then following that logic you'd have to conclude that Back in Black is in key of A, Panama is in key of A, etc. Try telling that to Angus or Eddie.

OTOH it worked for Skynyrd.