Rose item colors stem along with petal. Looks green at white (255,255,255), but not at the default dark red color.
Note: Should we just have a “Object Material/Coloring Bug Megathread” at this point? I’ve made a lot of reports similar to this, and it might be better for organization than to always be making new bug reports, especially considering the material regression oversights we’ve been having over the past year or so.