Pale Lichen vs Light Blue Green

How close are they?

ΔE 21.1, loose: different enough that you should pick on purpose. Light Blue Green is a little lighter, much more saturated, cooler than Pale Lichen.

Can I use Light Blue Green instead of Pale Lichen?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Light Blue Green is a little lighter, much more saturated, cooler than Pale Lichen.

Can I use Pale Lichen instead of Light Blue Green?

The same difference applies the other way round: Pale Lichen is a little darker, much more muted, 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.