Bright Yellow Green vs Lime Green

How close are they?

ΔE 19.8, loose: different enough that you should pick on purpose. Lime Green is noticeably darker, much more muted than Bright Yellow Green.

Can I use Lime Green instead of Bright Yellow Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Lime Green is noticeably darker, much more muted than Bright Yellow Green.

Can I use Bright Yellow Green instead of Lime Green?

The same difference applies the other way round: Bright Yellow Green is noticeably lighter, much more saturated.

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.