"The boys eat a black apple."
Translation:Les garçons mangent une pomme noire.
Noire is the female version of noir, not the plural.. but anyway, the colores do have a plural form to (noirs/noires), like in many other languages as spanish, italian or portuguese if i'm not wrong. Beside, english have plural colors too, but are used in a different way (for example: "this panting has a lot of reds" to refer to the variety of tones)
Wow I double failed. The second I came back to this post I saw it was wrong. But I understand the plural colors in english, there is a reason to differentiate between if there is one red or multiple different reds.
Technically this carries over to french because if there are multiple red apples, there are multiple reds on different apples. But I don't live in france so maybe sentences like this one are normal and "les garcons mangent les pommes noires" is a bad way of saying it.
I eat........Je mange; You eat.......Tu manges; He/She eats.......Il/Elle mange We eat.....Nous mangeons; You (formal) eat.......Vous mangez; They eat.....Ils/Elles mangent
Examples: Je mange une pomme. Tu manges une pomme. Il mange une pomme. Vous mangez une pomme. Nous mangeons une pomme. Ils mangent une pomme.
Hope that helps!