Assuming you are talking about Call of Duty:
The process for changing your spray in Call of Duty is actually quite simple. Just follow the steps below and you'll be good to go!
1) First, open up the game and head into the Create-a-Class menu.
2) Next, select the icon that represents your currently equipped weapon. For this example, we'll use an assault rifle.
3) Once you've selected your weapon, scroll down to the Attachment options and find the one labeled Spray. By default, this will be set to none.
4) To change your spray, simply click on the image next to Spray and select the new one you want from the menu that pops up. That's it! You've now successfully changed your spray in Call of Duty.