ΔE 13.7, fair: the same colour family, but not a straight swap. Hexed Lichen is a little lighter, warmer than Phthalo Blue RS.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Hexed Lichen is a little lighter, warmer than Phthalo Blue RS.
The same difference applies the other way round: Phthalo Blue RS is a little darker, 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.
See Phthalo Blue RS on the colour wheel See Hexed Lichen on the colour wheel
All matches: Phthalo Blue RS equivalents · Hexed Lichen equivalents