ΔE 11.9, fair: the same colour family, but not a straight swap. Ignis Fatuus is a little lighter, cooler than Dechala Lilac.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Ignis Fatuus is a little lighter, cooler than Dechala Lilac.
The same difference applies the other way round: Dechala Lilac is a little darker, 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.
See Dechala Lilac on the colour wheel See Ignis Fatuus on the colour wheel
All matches: Dechala Lilac equivalents · Ignis Fatuus equivalents