what's the difference between "The color gray and the color blue" and "A gray color and a blue color" within "Сірий колір і синій колір"?
As an English speaker, I see several ways this could be written, but it would depend on the context of the sentence. For example, if i was asked "What color is this?", I would reply "The color blue", or just "Blue" (we don't generally specify the word "color" because it is obvious that Blue is a color.) I definitely would NOT answer "The blue color" or "Blue color". If I was asked "What shade is teal?" Or "Describe teal", I might say "It is a blue color". However, I think it is much more common in English to use just the color name, or "the color <name>"
It should just be 'grey and blue'. As it is it sounds unnatural in English. This could be fixed given the context but as it stands it should just be 'grey and blue' or the grey and blue colour', but it is grammatically wrong as it is without an article.