Greenskin Flesh vs Bright Green

How close are they?

ΔE 18.6, loose: different enough that you should pick on purpose. Bright Green is a little lighter, more muted, warmer than Greenskin Flesh.

Can I use Bright Green instead of Greenskin Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Bright Green is a little lighter, more muted, warmer than Greenskin Flesh.

Can I use Greenskin Flesh instead of Bright Green?

The same difference applies the other way round: Greenskin Flesh is a little darker, more saturated, 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.