I'll give this an attempt at this:
1. Wrong. Name should be plural: NAMES
2. Wrong. Name should be plural: NAMES
3. Correct. I think. But a little strange.
4. Wrong. "boy car's" implies, strangely, that the car is a boy.
In truth, I don't like any of these sentences! But #3, I think, is the closest to correct.
I would rephrase the statement like this:
The boy's car is a beautiful colour.
This is much more clear and natural sounding to an English speaker, in my opinion