Would "The windshields are not tinted" be correct? If it's just a vocab test then ... whatever, but if referring to windshields in cars then we have tinted and not tinted, but nothing "coloured" and the word would be very unnatural.

Could you use "nuanțat" (instead of "colorate")?

In Britain, and relating to cars, we refer to "windscreens" not "windshields".

that's a very rare word to learn I believe

When it is a general statement, as it is the case now, we don't use the article"the". You simply say: Windshields are not colored.