If you need to mark a key Sugru is the perfect thing to do it
Step 1: Sugru Pack
Open a Sugru Pack of the color of your choice, wash your hands and take it out of its package.
Step 2: Shape Sugru Into the Key
Use your hands to soften the edges and make the Sugru for your key, then make sure that you leave some openings for the keychain ring and some openings for in case you want to remove the key color
Step 3: Finished
You are finished, leave it overnight and use it tomorrow before you go to work or school or wherever.
This guide was made at the Hacknight hosted by H3 Laboratories sponsored by Instructables and Sugru in El Paso, Texas.