Magmadroth Flame vs Ogre Brown

How close are they?

ΔE 22.2, loose: different enough that you should pick on purpose. Ogre Brown is a little darker, more muted than Magmadroth Flame.

Can I use Ogre Brown instead of Magmadroth Flame?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Ogre Brown is a little darker, more muted than Magmadroth Flame.

Can I use Magmadroth Flame instead of Ogre Brown?

The same difference applies the other way round: Magmadroth Flame is a little lighter, 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.