I have this script that makes brick change colors, but I wonder how can I make so the SpotLight inside the brick can change colors instead of brick? Here's my script:
while true do
script.Parent.Color = Color3.new (math.random (), math.random (), math.random () )
wait(1.5)
end

2 comments
You have everything you need right there, if I'm not mistaken. You just need to find the spotlight in the heirarchy (script.Parent takes you to what the script is stored in; where do you go from there?)
Also, I recommend checking out the wiki on what properties spotlights have, so that you know what the name of their color property is, among other things.