Dream On vs Ultramarine Blue

How close are they?

ΔE 18.0, loose: different enough that you should pick on purpose. Ultramarine Blue is noticeably darker, more saturated than Dream On.

Can I use Ultramarine Blue instead of Dream On?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Ultramarine Blue is noticeably darker, more saturated than Dream On.

Can I use Dream On instead of Ultramarine Blue?

The same difference applies the other way round: Dream On is noticeably lighter, 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.