Medium Sea Gray (RAF) vs Flanker Light Gray

How close are they?

ΔE 7.6, close: similar, with a visible difference side by side. Flanker Light Gray is a little darker, warmer than Medium Sea Gray (RAF).

Can I use Flanker Light Gray instead of Medium Sea Gray (RAF)?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Flanker Light Gray is a little darker, warmer than Medium Sea Gray (RAF).

Can I use Medium Sea Gray (RAF) instead of Flanker Light Gray?

The same difference applies the other way round: Medium Sea Gray (RAF) is a little lighter, 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.