Question

Where should the comma be in, The living room is painted a bright shiny red.

Answer 1

It should be between bright and shiny. The living room is painted a bright, shiny red. 

Answer 2

The living room is painted a bright, shiny red.

The comma should be placed after "bright" and before "shiny", leaving a space between them. The comma is used to prevent confusion.
I hope you find this the most helpful! :)