ΔE 12.0, fair: the same colour family, but not a straight swap. Satin Varnish is noticeably lighter than Metallic Medium. They are different kinds of paint: Pro Acryl Metallic Medium is a metallic and Vallejo Satin Varnish is a technical paint or medium, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Satin Varnish is noticeably lighter than Metallic Medium. They are different kinds of paint.
The same difference applies the other way round: Metallic Medium is noticeably darker.
ΔE is the colour difference between our two swatch estimates: under 2 is a perfect match (you’d struggle to tell them apart), under 6 very close, under 10 close, under 15 fair, under 20 loose, under 30 very loose, and 30 or more a poor match. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Metallic Medium on the colour wheel See Satin Varnish on the colour wheel
All matches: Metallic Medium equivalents · Satin Varnish equivalents