Are there any stencils or maps of colours on Pre-Beskar armour? From all I can see I may have to eye ball it using screen shots but I would like something more accurate.
Unfortunately - no. I'm putting together my own pre-beskar and the best I've found is forum posts stating that its a chesnutty brown. But looking over pics of suits from HERE it looks like they've used different shades of a chestnut brown to make areas stand out with wear and tear.
It's not a full template/damage map like the ones available for OT Bobas, but it gives confirmed matches for all the base paint colors (Montana Gold, available at art supply stores like Michael's or Blick).
As for the damage, most of the plates seem to show a base silver/dull aluminum with dark gray/weathered black edges (suggesting a primer layer over the metal base). There are also a lot of fine scuffs and light "grime" applied that give the finished armor a lot of depth and subtle variations up close, despite the relatively simple color scheme.
Best imagery I've seen of the pre-Beskar gear comes from the media section of this site, specifically the 2019 D23 display that had the full S1E1 outfit on display allowing a 360 walkaround. The only armor pieces/areas not well documented in those images are pieces like the kidney and back plates that are mosly hidden by other costume parts like the cape and bandolier.