ΔE 19.7, loose: different enough that you should pick on purpose. Umber Wash is a little lighter, much more muted, warmer than Hellion Red Wash.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Umber Wash is a little lighter, much more muted, warmer than Hellion Red Wash.
The same difference applies the other way round: Hellion Red Wash is a little darker, much more saturated, 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 Hellion Red Wash on the colour wheel See Umber Wash on the colour wheel
All matches: Hellion Red Wash equivalents · Umber Wash equivalents