Colour of Lumina are consumable items that grant one character a single Lumina Point.

Lumina Points are used to equip Luminas.
Think the Ability Gems from Final Fantasy IX. The more gems you have, the more abilities you can equip. It's the same concept here!

By the time you get to completing all of the side content, bosses, and superbosses (Act III), you will quickly find yourself lacking in the required Lumina Points that all those fancy character builds online need.

These are the single best items you can farm to power-up your team.
And you're going to want a LOT of them.

The easiest place to farm Colour of Lumina is at the top of the monolith at the end of Act II.



Fast Travel to the top of the monolith (Tower Peak), and then turn around to backtrack a little bit. You will grapple across a gap to a small alcove where a Clair Obscur enemy will be waiting.







Simply defeat it to receive 5 Colour of Lumina. At this stage, you should be able to defeat it rather easily. You'll also receive a weapon for Verso your first time, and behind it on a table is a weapon for Lune.

The gist is that you'll be able to fast travel to the flag, backtrack, cross the gap, kill the enemy, then run back to the flag to rest and respawn the target in around a minute or two. Repeat as needed/ad nausem until you get all the Lumina Points you need!

I hyperfocused one afternoon and wound up spending 5-6 hours farming...resulting in the following:

If you want to get REALLY crazy with this farm, then you need to go and pickup a very specific weapon for Verso - the Contorso.

Found at the Chosen Path:


It is acquired as a drop reward for defeating the Contortionniste enemy, encountered by interacting with the third painting on the right (bottom right).



This weapon has a "bug" that causes enemies to double their drops when it critically strikes them, visually shown as a beam zapping the enemy.




This means our target will drop 10 Colour of Lumina instead of 5!

There are other spots to farm, but this was the easiest I've found for our target item.
Best bang for your buck, so to speak.

Hope this helps and I hope you enjoy the game!