ΔE 15.7, loose: different enough that you should pick on purpose. Motherlode is a little lighter, more saturated than Mithril.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Motherlode is a little lighter, more saturated than Mithril.
The same difference applies the other way round: Mithril is a little darker, more muted.
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 Mithril on the colour wheel See Motherlode on the colour wheel
All matches: Mithril equivalents · Motherlode equivalents