Red things can be crimson, scarlet, vermilion, maroon, pink or even salmon.
Green things are just green.

Why ?

emerald, lime, …….

khaki
lime
pea
sea
candy apple
emerald
jade
olive
teal
moss
mint

etc.

lovat

Hmmm, OK, there’s a couple I missed there, but most of them are prefixes for the word green.
Lime green, pea green, etc.
Nobody would say they’re going to buy a tin of pea paint.

Surely nobody would call pink, salmon or maroon ‘red’?

red……pink
chalk……cheese

snot
sarah

What about bright red and bright green?

Pink is pale red, maroon is dark red.
There are no corresponding word for blue, yellow or green.

what about hideously dull thread and hideously dull green?

A thread is only as dull as the people who post on it. 😉

While we’re on the subject of colours, why is white not always white? Try colour matching white Fords when they have 7+ possibilities under the same name. It could, and did, confuse a stupid person.