Flash Gitz Yellow vs Yellow Green

How close are they?

ΔE 19.9, loose: different enough that you should pick on purpose. Yellow Green is a little darker, cooler than Flash Gitz Yellow.

Can I use Yellow Green instead of Flash Gitz Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Yellow Green is a little darker, cooler than Flash Gitz Yellow.

Can I use Flash Gitz Yellow instead of Yellow Green?

The same difference applies the other way round: Flash Gitz Yellow is a little lighter, warmer.

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.