relative minors

OK so if oyur playing in the key of Amajor then you can use all Amajor scales, and F# minor scales becuase thats its relative minor...right?? OK so my question is, all the BLUES scales that are scattared around this site are ore or less PENITONIC MINOR scales. And you mark them all as the root of the scale being the key its in, but technically, couldn't you only ( creativity aside, in therory im meaning) play you G BLUES scale with a song in the key of A#??, i dunno, cuz in all of the post the keys are the same as the root, and i was taught that a minor scale was in the key of its relative major. Teach me!

Yes. Blues scales are pentatonics with an added note; b5 for minor, and b3 for major. One thing to notice in relative keys is this is the same note. In A minor, Eb is the b5. The relative major of A minor is C major, the b3 is Eb. The way you configure these keys with each scale, creates different styles. In Blues, the blues minor is used exclusively. Over an A minor chord, you would use the A blues minor scale. Here's the difference, if you have a C major chord. You use a C minor blues scale over the the C major chord. This produces a b3 over that chord naturally. C minor pent has an b3 or in this case Eb. What is added is additional b5 (Gb), what we call the "blues note". It's called that because regardless if it's played over a major or minor chord, it still sounds bluesy. This is done alot in rock also, although the b5 is exceptional. One thing that doesn't work very well is playing a A major blues over a A minor chord. The other config is playing a C major blues over a C major chord, this is done alot in country music.