Mana Regeneration vs Wagram Blue

How close are they?

ΔE 40.1, loose: different enough that you should pick on purpose. Wagram Blue is noticeably darker, much more muted than Mana Regeneration.

Can I use Wagram Blue instead of Mana Regeneration?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 40). Wagram Blue is noticeably darker, much more muted than Mana Regeneration.

Can I use Mana Regeneration instead of Wagram Blue?

The same difference applies the other way round: Mana Regeneration is noticeably lighter, much more saturated.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.