ΔE 17.1, loose: different enough that you should pick on purpose. Deep Blue is a little darker, warmer than Shadow Thorn.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Deep Blue is a little darker, warmer than Shadow Thorn.
The same difference applies the other way round: Shadow Thorn is a little 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.
See Shadow Thorn on the colour wheel See Deep Blue on the colour wheel
All matches: Shadow Thorn equivalents · Deep Blue equivalents