words - Confirmation regarding Japanese colors i-adjective

I want to ask confirmation regarding Japanese colors. I understand that there are NOUN, and I-adj version of some colors. Such as 赤＆赤い, 青＆青い, etc.

But this part below is something I cannot confirm. Some article say that it is okay to say both "車は赤です" and "車は赤いです", but some say that you can only say "車は赤です". Which one is correct?

Also about basic colors. It seems that green (緑) and purple (紫) don't have i-adj version. But how about yellow (黄色), brown (茶色), orange (橙色) & grey (灰色)? Do they have i-adj version? I'm pretty sure I've heard 黄色い and 茶色い, but wasn't sure about 橙色い and 灰色い...

Update for specific reference I read about:
This sentence is copied from Link:

"It might be possible to use 赤いです [akai desu] in simple sentences, but I know that 赤です [aka desu] is always safe."

And this one is copied from Link:

"ボールはしろです. The ball is white. When using primary colors to modify a noun, use the i-adjective form; otherwise, use the no-adjective form."

Answer

Could you be more specific about the article you talk about? In English obviously "red" could be both a noun or an adjective..wait, maybe is not so obvious.

Anyway, according to this source, there are six colors in Japanese that are い-adjectives:

「赤い」, ｢青い」,「白い」,「黒い」,「黄色い」, 「茶色い」.

On the other hand, colors such as 「緑」,「金」,「ピンク」,「オレンジ」and so on, are actually names belonging to the category of so-called の-adjectives.

EDIT: a related question on の-adjectives is here.

Moreover, always according to the first source, you can actually remove the い from the former six adjectives. This would turn them into names/の-adjectives as well.

To recap, for example 赤い and 赤(の) are both adjectives, while there is no such thing as 緑+い for example.

Edit: I am not sure why in the article he says that 車は赤です is safe, as the author does not provide any specific grammatical explanation. It might be related to い-adjective + です (there is a lot on this argument at this link). I do not think it has anything to do with being or not an adjective as both 赤 and 赤い are (since a の-adjective is nothing but a name that usually in English is translated with an adjective).