How to define the character's head?

So I am trying to make a 2d platformer where the character can change colour by pressing certain keys. I am currently trying to figure out how to find the character as game.Players.LocalPlayer.Character says it's a nil value. I then went to the Dev Hub and found the character page. I changed to a local script and changed to player.Character and still no luck as player is unknown. Here is a small part of the code I am working with:

if player.Character.Head.BrickColor == BrickColor.new("Really red") then
	script.Parent.BrickColor = BrickColor.new("Really red")
end

I also have the code in a LocalScript inside of a Part in workspace. Any sort of help would be appreciated!

You cannot put a LocalScript in a part in workspace. Put the LocalScript in StarterPack and define part (e.g. local Part = game.Workspace.Part). The Player can be called by LocalScript in StarterPack using game.Players.LocalPlayer or script.Parent.Parent. Also if you want to detect a player's head color, you cannot use BrickColor.new("really red") because the color is not changed.

if player.Character.Head.BrickColor then
	script.Parent.BrickColor = BrickColor.new("Really red")
end

Let me explain the code above and why is it like that. So i assumed you have already set the player's head color to really red, or maybe you are going to change it in a script. If you did not, you will have to change the player's head color yourself. So explanation: if the player's head color is "Really Red" (if player.Character.Head.BrickColor then), then the Part's color will change, does that make sense to you?

This is simple! Just use this!

for i,v in pairs(game.Players:GetChildren()) do
if v.Character and v.Character:FindFirstChild("Head") then
{CODE}
end

LocalScripts that are cloned from StarterGui or StarterPack into a player’s Backpack or PlayerGui are often run before the old Character model is deleted. You're supposed to do:

if not character or not character.Parent then
    character = game.Players.LocalPlayer.CharacterAdded:wait()
end

Then you define character after the if statement. I hope this helps :)