Barren Yellow vs Mars Orange

How close are they?

ΔE 17.0, loose: different enough that you should pick on purpose. Mars Orange is a little lighter, more saturated than Barren Yellow.

Can I use Mars Orange instead of Barren Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Mars Orange is a little lighter, more saturated than Barren Yellow.

Can I use Barren Yellow instead of Mars Orange?

The same difference applies the other way round: Barren Yellow is a little darker, more muted.

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.