Question

What is the problem with the following sentence ? He want to give me a bright red car

Answer 1

That there should be a "s" at the end of want to make the sentence make sense

Answer 2

In order for the sentence to be correct, want would need to be wants.
"He wants to give me a bright, red car."
He is reffering to one person.
You could also change the sentence to, "They want to give me a bright, red car."
As you can see, you also need a comma between bright and red.