"its supposed to change the colour of my selected parts in a folder but wont work it supposed to change them to yellow for 5 seconds then revert back to their original colour plase fix"

The script seems correct, but there are a few things you can check to ensure it works as expected:

1. Ensure that the product ID is correct. The product ID in the script should match the ID of the product you have created in Roblox.

2. Make sure that the parts you want to change the color of are actually in a folder named "SelectedParts" in the Workspace.

3. Check if the event `PromptProductPurchaseFinished` is being triggered. This event is fired when a player has finished purchasing a product. If the product purchase process is not completed, the event will not be triggered, and the color of the parts will not change.

4. Ensure that the parts in the "SelectedParts" folder are BaseParts. The script only changes the color of objects that are BaseParts.

5. Make sure you have the necessary permissions to change the color of the parts. If you don't have the required permissions, the script will not be able to change the color of the parts.

If everything is set up correctly, the script should change the color of the parts in the "SelectedParts" folder to bright yellow for 5 seconds, then revert them back to their original color.