Eidolon Purple Clear vs Pastel Violet

How close are they?

ΔE 19.7, loose: different enough that you should pick on purpose. Pastel Violet is noticeably lighter, much more muted than Eidolon Purple Clear.

Can I use Pastel Violet instead of Eidolon Purple Clear?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Pastel Violet is noticeably lighter, much more muted than Eidolon Purple Clear.

Can I use Eidolon Purple Clear instead of Pastel Violet?

The same difference applies the other way round: Eidolon Purple Clear 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.