At least some of the Modron tribe seem to have misassigned materials in the Beastiary.
I only know three of them currently but it is as follows:
Bio Bot → Bio Scrap
Seems correct and material colors match.
Sentry Bot → Shield Scrap
Thematically appropriate but no color match. Seems closer to Wizard’s Defender’s body colors.
Wizard’s Defender → Sentry Scrap
This seems to belong to Sentry Bot and matches Sentry Bot’s color palette.