This is very similar to this question. You can read more there for more perspective on this problem.

while uses a condition -- something that is either true or false -- to decide to stop or keep going. Touched doesn't give you anything like that -- an event is just a point in time, but it doesn't give you a way to ask "is this part still touching"

There's a corresponding TouchEnded event, though, that you can use.

local brick = script.Parent
-- When you find yourself repeating yourself, something's amiss
-- Use variables to shorten things!

function startTouch()
	brick.BrickColor = BrickColor.new("Bright red")
end

function endTouch()
	brick.BrickColor = BrickColor.new("Institutional white")
end
brick.Touched:connect(startTouch)

This is a very simple first solution to this problem. As with the other question, there are problems with it:

• if any part, not just the original touching part, stops touching the button, it goes back to white

We can fix that using the same techniques from that other question

Using GetTouchingParts

I have never used GetTouchingParts -- I'm hoping it works as expected.

Since we the color to always represent whether or not it's being touched, we need something that is always working. We can make a while true do loop to make a loop that will never stop working.

local brick = script.Parent

while true do
	wait() -- Breathing room
	-- otherwise it's too eager and will kill ROBLOX

	local partsTouching = brick:GetTouchingParts()
end

We act based on whether or not there are any parts touching it. partsTouching is a list -- there is nothing touching it if that list is empty. We can check if it's empty by seeing if its length is equal to 0:

local brick = script.Parent

while true do
	wait() -- Breathing room
	-- otherwise it's too eager and will kill ROBLOX
	if #partsTouching == 0 then
		brick.BrickColor = BrickColor.new("Institutional white")
	else
		brick.BrickColor = BrickColor.new("Bright red")
	end
end