Baron Blue vs Glazier Blue

How close are they?

ΔE 21.8, loose: different enough that you should pick on purpose. Glazier Blue is noticeably lighter, much more muted than Baron Blue.

Can I use Glazier Blue instead of Baron Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Glazier Blue is noticeably lighter, much more muted than Baron Blue.

Can I use Baron Blue instead of Glazier Blue?

The same difference applies the other way round: Baron Blue is noticeably darker, 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.