The pentatonic first position for instance can be a good indicator, your index finger is on the root note for a minor and your pinky is on the root note for major, so for example you’re in the a pentatonic shape, fifth fret, start on that note (A) for a minor solo, or the pinky (8th fret) for a c major solo, just emphasise the root note, minor or major.
Position will always be determined by the root note of the scale. The scale diagrams on this website show the root notes as a black dot or an ‘R’.