This game has 25 unlockable colour schemes, costing a grand total of 10000 crystals. These colour schemes can be accessed by clicking the little crystal icon in the bottom-left corner of the main menu. Each crystal you collect in-game will be added to a grand total which cannot be deducted from by any means short of save editing. At the end of each run, the total amount of crystals you've collected will be displayed alongside the milestone you must reach in order to unlock the next colour scheme. Below, I've collated images of each colour scheme in order of accessibility, including the name and price of the respective unlock.