Music Banter - Mixolydian scale- when to play?

Currently I'm learning blues guitar and I've been learning the essential scales, pentatonic and blues. I'm looking to expand my guitar vocabulary for improvisations.

My basic question is- Do you have to play the Mixolydian scale over the root chord of the song progression or can it be played at any time? The good thing about the minor pentatonic and blues scales is that they can be played at any time and still sound good. The major pentatonic however should only be played over the root chord, that is only play the A major pentatonic over the A chord part of the song. It sounds awful if you play the A major pentatonic scale over the D chord for example. (I'd give a link but I need more posts here to do that. Search Youtube for "Are you guilty of hitting this awful note? Learn how to use the Major Pentatonic In A Blues!" for an audible example)

So that's the major pentatonic understood. But what about the Mixolydian scale, can it be played anytime like the minor pentatonic scale, or is a strictly "root chord only" scale like the major pentatonic? I'm hoping to inject a brighter sounding scale into my impovs, and the Mixolydian will hopefully do that for me.

I've asked the question before on another website but just got a couple of long winded answers that didn't really answer my question and mainly seemed to be about showing off the answerer's music knowledge. I'm hoping for a fairly basic "yes you can" or "no you can't" type answer!