That difference in Thunderbolt bandwidth is annoying, but there's no standard color or symbol to indicate it, so marking the port would at most vaguely signify

That difference in Thunderbolt bandwidth is annoying, but there's no standard color or symbol to indicate it, so marking the port would at most vaguely signify that some difference exists, which is less useful. Apple has never shipped a laptop with both USB 2.0 and USB 3.0 ports, which is what the blue convention is for.