LatextTest

Based on below tests and tried with different themes, the best option would be SVG, only in Dark theme it's not visible and in Dimmed it's not that readable. So maybe better is still the PNG black on white version although is not scalable it's good enough when you zoom in.

Black on Black (doesn't work very well with Default Dark Theme)

GIF version (lower quality / doesn't render very nice):

PNG version (better quality than GIF):

SVG version (resolution independent / difficult to see with Dark and Dimmed theme):

Black on White version (works with Default Black/White/Dimmed themes used on e.g. Github and StackOverflow)

GIF version(lower quality):

PNG version (better quality than GIF):

SVG version (resolution independent, but does not support black on white?!):