Underbelly Blue vs Insignia White

How close are they?

ΔE 15.2, loose: different enough that you should pick on purpose. Insignia White is a little lighter, more saturated than Underbelly Blue.

Can I use Insignia White instead of Underbelly Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Insignia White is a little lighter, more saturated than Underbelly Blue.

Can I use Underbelly Blue instead of Insignia White?

The same difference applies the other way round: Underbelly Blue is a little darker, more muted.

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.