ΔE 34.9, loose: different enough that you should pick on purpose. Lemon Yellow is a little lighter, much more muted, cooler than Flash Gitz Yellow.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 35). Lemon Yellow is a little lighter, much more muted, cooler than Flash Gitz Yellow.
The same difference applies the other way round: Flash Gitz Yellow is a little darker, much more saturated, 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.
See Flash Gitz Yellow on the colour wheel See Lemon Yellow on the colour wheel
All matches: Flash Gitz Yellow equivalents · Lemon Yellow equivalents