RAL 3003 Ruby Red is a type of color that is used to paint things. It is a very special color of red that looks a little bit like a ruby or a very shiny red jewel.
"RAL" is just a fancy name for a group of people who came up with a special set of colors that lots of people use when they want to paint something. They picked a number, 3003, to help people know which exact color of red they mean when they say "RAL 3003."
So, when someone says "RAL 3003 Ruby Red," they are talking about a specific shade of red that is used in painting things like cars, houses, furniture, and many other things.