Dechala Lilac vs Purple

How close are they?

ΔE 15.2, loose: different enough that you should pick on purpose. Purple is noticeably darker, warmer than Dechala Lilac.

Can I use Purple instead of Dechala Lilac?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Purple is noticeably darker, warmer than Dechala Lilac.

Can I use Dechala Lilac instead of Purple?

The same difference applies the other way round: Dechala Lilac is noticeably lighter, cooler.

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.