How to make a GUI change color when you touch a brick?

Note that this ain't a request site, you have to try to solve your problem first before you ask here. However since your new I'll help you out this once.

In the gui that you want to change color, insert a local script with the following script:

game.Workspace:WaitForChild("ColorPart",10) -- waits for a part in workspace called ColorPart and if it doesn't appear in 10 seconds, it will stop waiting and continue with the script. (Make sure there actually is a part in workspace called ColorPart.

--Variables (to shorten the script a bit and make it easier)
local Part = game.Workspace.ColorPart
local plr = game.Players.LocalPlayer -- NOTE: LOCALPLAYER ONLY WORKS ON LOCAL SCRIPTS

Part.Touched:Connect(function(hit) --fires a function when ColorPart is Touched by something
    if hit.Parent.Name = plr.Name then -- checks if the thing that touched's name is your username to confirm it is you who touched it
        local something = script.Parent
        something.BackgroundColor3 = Color3.fromRGB(0,127,255) -- this changes the gui's color to azure color, mess around with the rgb scale all you want. If you want to use the HSV scale instead then change fromRGB to fromHSV.
    end
end)

The youtube tutorials are outdated. We use PlayerGui for now. Accessing PlayerGui needs LocalPlayer so you need to use LocalScript.

Example:

local gui = game.Players.LocalPlayer:WaitForChild("PlayerGui").Frame

game.Workspace.Part.Touched:Connect(function()
    gui.BackGroundColor3 = Color3.new(0,0,255)
end)

Assuming you want it to change locally, here is how I would go about scripting it.

First off I would define every variable we need.

local part = script.Parent -- if script isn't being put in part change this to the path of the part
local plr = game:GetService("Players").LocalPlayer -- only works in a local script
local plrgui = plr:WaitForChild("PlayerGui")
local gui = -- path to gui, can be started using plrgui then probably followed by a screengui and frame of some kind

Second, we can use the part.touched function to get when a part is hit,

part.Touched:Connect(function(hit --[[hit is equal to what is touching it when this is ran]])
    -- everytime this part is touched, the code inside this will be ran
end)

since you want it to happen everytime a player is hit we have to make sure the code is only being ran when hit is a player

part.Touched:Connect(function(hit)
    if hit.Parent:FindFirstChild("Humanoid") then
        --[[now any code here wont be ran unless "hit" has a humanoid in its parent like a player model]]
    end
end)

Now that we have the player that hit it, we can run the code to change the color of a gui.

part.Touched:Connect(function(hit)
    if hit.Parent:FindFirstChild("Humanoid") then
        gui.BackgroundColor3 = Color3.new(0,255,0) --sets color to blue
    end
end)

That's all, at the end your code should look something like this

local part = script.Parent -- if script isn't being put in part change this to the path of the part
local plr = game:GetService("Players").LocalPlayer -- only works in a local script
local plrgui = plr:WaitForChild("PlayerGui")
local gui = -- path to gui, can be started using plrgui then probably followed by a screengui and frame of some kind

part.Touched:Connect(function(hit)
    if hit.Parent:FindFirstChild("Humanoid") then
        gui.BackgroundColor3 = Color3.new(0,255,0) --sets color to blue
    end
end)

Hope this helped you!!! If you don't understand anything add me on discord (actz#2196) and I can go over it with you.