How do I make someones decal change then change back?

So I'm guessing you want to change the face, so here is something that might work. Put this as a localscript in starterplayerscripts(I think).

wait(.1) -- lets player spawn in

local playerName = game.Players.LocalPlayer.Name -- used to get player from workspace
local playerFace = game.Workspace.playerName.face -- gets the face of the player
local blinkFace = "PUT FACE URL TEXTURE/DECAL HERE" -- the blinking face
local normalFace = playerFace.Texture -- the face the person spawned with but if you want to set a face you can replace playerFace.Texture with "url of face here" with the quotation marks

while true do -- loops the blink infinitly
	playerFace.Texture = blinkFace -- makes person blink
	wait(.1) -- blinks for 1 second
	playerFace.Texture = normalFace -- goes back to normal face or unblink
	wait(10) -- waits 10 seconds before blinking again
end -- end of the loop

This script will change someones face for .1 of a second every 5 seconds. You can change that up there. If you like my answer please remember to thumbs up :D.