ΔE 15.3, loose: different enough that you should pick on purpose. Skrag Brown is a little darker, more muted, warmer than Amaranth Red.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Skrag Brown is a little darker, more muted, warmer than Amaranth Red.
The same difference applies the other way round: Amaranth Red is a little lighter, 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 Amaranth Red on the colour wheel See Skrag Brown on the colour wheel
All matches: Amaranth Red equivalents · Skrag Brown equivalents