If your blue doesn't look right on your dark background, why are you using that blue?
If your yellow doesn't look right on your light background, why are you using that yellow?
I mean i get how this can be a problem with hard-coded arbitrary values — you can't ever guarantee that e.g. #ff6600 will go with anyone's particular colour scheme. But these 8 or 16 standard colours are not hard-coded, they're configurable in every terminal i've ever used, including Windows's shitty command prompt. They can and should be set to a value that's appropriate for your background and text colours.
Maybe this is more a fault of the terminal/theme developers for providing unusable defaults. idk.