card number/color

[Mooncalf]

I just noticed in the top right of every card picture there's a colored circle and number.

Any idea what they mean? 

I think the color corresponds to the monster's element, but then what does the number mean?

[Rachella]

The color I believe does indeed correspond to the element of the monster.

As far as the number.. No idea. Is the number the same for all monster cards of a particular color? Or different for each and every one?

Perhaps it's for identifying purposes?

[Mooncalf]

I like that.

Little detailed touches like that make this game worth playing.

[Combo]

Arent there like undead 1,2,and 3?

[Aena]

There are different number types for each monster element, like what Judgement's saying... but not sure if that has anything to do with it?
Compare it with a monster database, maybe?