TS: Prefer union arguments to overloads for simple cases

[willstott101]

This works around microsoft/TypeScript#14107

In my typescript project I accept config for colors as color: string | number but using that with threejs can be a fiddle in some cases:

  Overload 2 of 3, '(color: number): Color', gave the following error.
    Argument of type 'string | number' is not assignable to parameter of type 'number'.
      Type 'string' is not assignable to type 'number'.
  Overload 3 of 3, '(color: string): Color', gave the following error.
    Argument of type 'string | number' is not assignable to parameter of type 'string'.

I searched the codebase for overloads using ( +)(\w+)\(.+\n\1\2\( and it looks like Color is pretty much the only unnecessary use of overloads so have fixed all those which I found.

I cannot see any typescript tests besides lint so I have't tried to add any.

[mrdoob]

That'll teach me to not do this kind of things in the APIs 😅

[mrdoob]

Thanks!