I have a brick that is supposed to change colors to red using Color3.new() but it's not working.
local Brick = script.Parent Brick.Color3 = Color3.new(255,0,0)
The problem you are having is VERY simple.
Instead of using Color3.new, use Color3.fromRBG() which uses Red Green and Blue instead.
local Brick = script.Parent Brick.Color3 = Color3.fromRBG(255,0,0)