Stormhost Silver vs Motherlode

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Motherlode is a little lighter, more saturated than Stormhost Silver.

Can I use Motherlode instead of Stormhost Silver?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Motherlode is a little lighter, more saturated than Stormhost Silver.

Can I use Stormhost Silver instead of Motherlode?

The same difference applies the other way round: Stormhost Silver 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.