Imp Yellow vs Titanate Yellow

How close are they?

ΔE 23.3, loose: different enough that you should pick on purpose. Titanate Yellow is noticeably lighter, more saturated, cooler than Imp Yellow.

Can I use Titanate Yellow instead of Imp Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Titanate Yellow is noticeably lighter, more saturated, cooler than Imp Yellow.

Can I use Imp Yellow instead of Titanate Yellow?

The same difference applies the other way round: Imp Yellow 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.