Mythical Orange vs Khador Red Base

How close are they?

ΔE 19.8, loose: different enough that you should pick on purpose. Khador Red Base is a little darker, more saturated, cooler than Mythical Orange.

Can I use Khador Red Base instead of Mythical Orange?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Khador Red Base is a little darker, more saturated, cooler than Mythical Orange.

Can I use Mythical Orange instead of Khador Red Base?

The same difference applies the other way round: Mythical Orange is a little lighter, more muted, warmer.

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.