How this works in some other games I've played:
Warframe (F2P) - You buy palettes of colors with microtransactions. (Some palettes are given away for seasonal events.) Palettes come with around 60 colors each, and sell for like $1 in real money. Changing colors on your equipment is free and unlimited.
Guild Wars 2 (B2P) - Dyes are found, gathered, crafted or bought. Once you unlock a dye color, you have access to it permanently. Changing colors on your equipment is free and unlimited.
Final Fantasy 14: ARR (MMO w/sub) - Pots of dye are bought from vendors or crafted. Pots of dye can only be used once, and are consumed upon coloring an item.
Destiny 1 (B2P w/microtransactions) - Shaders are found, bought from vendors, or are rewards from certain activities and in-game achievements. You can only carry a limited amount of Shaders on you at a time, but all Shaders you've unlocked are available from an in-game kiosk at no charge. Shaders color all your equipment at once, but changing Shaders is free and unlimited.
Contrast that now with D2:
Destiny 2 (B2P w/microtransactions) - Currently, Shaders are found as random drops or as part of microtransactions. Each separate piece of equipment can be shaded separately, but Shaders are consumed upon use. There is no kiosk or way to re-get Shaders outside of random drops or microtransactions.
Essentially, it takes the Final Fantasy 14: ARR system and strips out all the easy ways (read: vendors) to get Shaders. No unlocks, no kiosks, just more RNG.