Dechala Lilac vs Smalt Hue

How close are they?

ΔE 17.2, loose: different enough that you should pick on purpose. Smalt Hue is a little darker, cooler than Dechala Lilac.

Can I use Smalt Hue instead of Dechala Lilac?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Smalt Hue is a little darker, cooler than Dechala Lilac.

Can I use Dechala Lilac instead of Smalt Hue?

The same difference applies the other way round: Dechala Lilac is a little lighter, 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.