Oozing Vomit vs Mustard Yellow

How close are they?

ΔE 16.9, loose: different enough that you should pick on purpose. Mustard Yellow is noticeably darker, warmer than Oozing Vomit.

Can I use Mustard Yellow instead of Oozing Vomit?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Mustard Yellow is noticeably darker, warmer than Oozing Vomit.

Can I use Oozing Vomit instead of Mustard Yellow?

The same difference applies the other way round: Oozing Vomit is noticeably lighter, cooler.

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.