Scales to Play Over G#6/9
Every chord is a subset of several scales: any scale that contains all of a chord's tones fits over it. Pick a chord to see the matching scales from its own root, the major keys the chord belongs to, and full fretboard diagrams for every scale on guitar.
A G#6/9 chord contains the notes G# – A# – B# – D# – E#. Any scale that includes every one of those 5 tones fits over it — from the root G#, that means G# Major, G# Major Pentatonic, G# Rock 'n' Roll, G# Lydian, G# Mixolydian, G# Dorian Bebop and G# Mixolydian Bebop. They differ only in the notes between the chord tones, and that is where each scale gets its color.
G#6/9 is also diatonic to 3 major keys: Db major (relative minor Bbm), Eb major (relative minor Cm), Ab major (relative minor Fm). In a song from one of those keys you can also solo with the key's own major scale or its relative minor pentatonic across the whole progression, not just this chord.