Charming Chartreuse vs Estus Yellow

How close are they?

ΔE 20.8, loose: different enough that you should pick on purpose. Estus Yellow is a little lighter, much more muted, warmer than Charming Chartreuse.

Can I use Estus Yellow instead of Charming Chartreuse?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Estus Yellow is a little lighter, much more muted, warmer than Charming Chartreuse.

Can I use Charming Chartreuse instead of Estus Yellow?

The same difference applies the other way round: Charming Chartreuse is a little darker, much 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.