Russ Grey vs Blue Base

How close are they?

ΔE 19.5, loose: different enough that you should pick on purpose. Blue Base is noticeably darker, more saturated, warmer than Russ Grey.

Can I use Blue Base instead of Russ Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Blue Base is noticeably darker, more saturated, warmer than Russ Grey.

Can I use Russ Grey instead of Blue Base?

The same difference applies the other way round: Russ Grey is noticeably lighter, more muted, 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.