Lothern Blue vs Light Blue

How close are they?

ΔE 17.4, loose: different enough that you should pick on purpose. Light Blue is noticeably lighter, more saturated, cooler than Lothern Blue.

Can I use Light Blue instead of Lothern Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Light Blue is noticeably lighter, more saturated, cooler than Lothern Blue.

Can I use Lothern Blue instead of Light Blue?

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