✓ Accepted answer
Your Problem
When you store the 10 random BrickColors in your colors table, they are already BrickColor datatypes. So this means that line 11 is like saying BrickColor.new( [BrickColor] ) which doesn't work.
Your error
There is a constructor that allows you to input Color3 datatypes as arguments for the BrickColor.new function, which is why you recieved the error :)
How to fix
If you apply some logical operators, as well as the type function you can easily get passed this.
The type function returns the datatype of the given value. You can check if the current iteration is either one of your manually inputted strings or a randomly added value, and go about setting the BrickColor property accordingly.
workspace.Baseplate.BrickColor = (type(v) == "string" and BrickColor.new(v)) or v
2 comments
Maybe this results to BrickColor.new(BrickColor.Random()) ?
No, the same error still occurs