Golfag Brown vs Mars Yellow

How close are they?

ΔE 18.0, loose: different enough that you should pick on purpose. Mars Yellow is a little lighter, more saturated than Golfag Brown.

Can I use Mars Yellow instead of Golfag Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Mars Yellow is a little lighter, more saturated than Golfag Brown.

Can I use Golfag Brown instead of Mars Yellow?

The same difference applies the other way round: Golfag Brown 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.