>>57987426
It's more complicated than that, even if both of them keep all their clothes on. Because like Sapphire, Ruby changes his clothes a lot but his visual differences compared to his game counterparts are much more subtle. And that's without taking into account different fanartists' art styles (where they might ignore Yamamoto's very specific eye shapes style, or how some people draw game/anime May with fangs as a style choice, and others somehow forget to draw Sapphire's fangs)

The easiest hint is that Ruby and Sapphire's clothes nearly always match. Because Ruby's so down bad he keeps tailoring these matching couple outfits. So usually if Sapphire is wearing her Emerald alt outfit (the blue one), if Ruby's there too then he should also be in his Emerald alt outfit (the red one).

But since Ruby's clothes change less dramatically than Sapphire's, fanartists mix up Ruby's clothes more often. Can't blame them because even Yamamoto accidentally colored Ruby's headband wrong once (green instead of red in an Emerald arc panel) and some Twitter autist had to correct him.

And yeah Yamamoto's art is only getting worse unfortunately