Cygnar Blue Base vs French Blue

How close are they?

ΔE 25.8, loose: different enough that you should pick on purpose. French Blue is a little darker, much more muted, cooler than Cygnar Blue Base.

Can I use French Blue instead of Cygnar Blue Base?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). French Blue is a little darker, much more muted, cooler than Cygnar Blue Base.

Can I use Cygnar Blue Base instead of French Blue?

The same difference applies the other way round: Cygnar Blue Base is a little lighter, 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.