Disgusting Slime vs Bismuth Yellow

How close are they?

ΔE 37.6, loose: different enough that you should pick on purpose. Bismuth Yellow is noticeably lighter, more saturated, warmer than Disgusting Slime.

Can I use Bismuth Yellow instead of Disgusting Slime?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 38). Bismuth Yellow is noticeably lighter, more saturated, warmer than Disgusting Slime.

Can I use Disgusting Slime instead of Bismuth Yellow?

The same difference applies the other way round: Disgusting Slime is noticeably darker, more muted, 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.