After completing the first level and arriving at Psychonauts headquarters in the main lobby there will be a Otto-matic shop next to the entrance to the noodle Bowl in which you can buy pins with Psitanium. There should be purple sparkling patches in the main lobby which you can interact with to earn Psitanium. On your first visit to the shop you'll be allowed to purchase a pin for free which changes the colour of your Levitation balloon power (equipping multiple colour changing modifiers will combine the colours together). There are 3 of these pins, simply choose one to buy for 0 Psitanium then buy the other two pins for 10 Psitanium each and once you have equipped them all the achievement should unlock.