The "Touched" event

All BaseParts have an event that is fired when that part comes in contact with another part:

local part = --insert part path here
part.Touched

How to use the event?

There are two ways of having code running upon the event firing. In RBX.Lua, most, if not all events, have two useful methods:

A) Event:wait()

This method will basically stop the script until the event in question is fired. It can be useful if you are looking to run the code in question only a couple times. The syntax for it is:

part.Touched:wait() -- yield the script until this part touches another part

-- place code here

However, for your case, I am 99.999999% sure this won't be the best. If your part touches a part that is not the desired one, the code will run anyways.

B) Event:Connect()

This method is self-explanatory. It will connect something to that event. That something is a function (a function is a code snippet, basically). :Connect() does not yield. If the event is fired twice, the code will run twice. So:

part.Touched:Connect(OneFunction)

There are two ways to do a connection:

B.1) Anonymous function

In this way, you will be declaring the function itself when you are connecting it to the event:

part.Touched:Connect(function()
    -- code here
end)

This is best used if you are going to use this code snippet only once in the whole script.

B.2) Declare a local/global function before connecting it.

In this way, you will be declaring the function itself before connecting it to the event:

function f()
    -- code here
end

part.Touched:Connect(f)

The advantage of this one is that you can connect the same function to different events or even call the function itself, saving some lines:

part.Touched:Connect(f)
part1.Touched:Connect(f)
part2.Touched:Connect(f)

C) Parameters passed by the event

Some events, when fired, and when there's a function connected to them, will pass values as parameters. Those values can be used by the function to help execute the code. In the case of the Touched event, it passes the part the other part came in contact with:

part.Touched:Connect(function(otherPart)
    -- code here
    -- you can use the "otherPart" variable as the other part.
end)

function onContact(otherPart)
    -- code here
    -- you can use the "otherPart" variable as the other part.  
end

part.Touched:Connect(onContact)

In this case, you can use otherPart.Material and otherPart.BrickColor

Hope I helped!

~dav1000999