Dechala Lilac vs Bluebird Grey

How close are they?

ΔE 27.7, loose: different enough that you should pick on purpose. Bluebird Grey is noticeably darker, much more muted, cooler than Dechala Lilac.

Can I use Bluebird Grey instead of Dechala Lilac?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 28). Bluebird Grey is noticeably darker, much more muted, cooler than Dechala Lilac.

Can I use Dechala Lilac instead of Bluebird Grey?

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