ΔE 18.7, loose: different enough that you should pick on purpose. Ruby Red is a little darker, much more saturated, cooler than Ruddy Umber.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Ruby Red is a little darker, much more saturated, cooler than Ruddy Umber.
The same difference applies the other way round: Ruddy Umber is a little lighter, much more muted, 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 Ruddy Umber on the colour wheel See Ruby Red on the colour wheel
All matches: Ruddy Umber equivalents · Ruby Red equivalents