Every value plot_masks(), plot_boxes(), overlay_mask() and overlay_agreement() use when you do not give them one: which colours mean found, missed and invented, one colour per class for plot_anchors(), how much of the image an overlay lets through, how a box is labelled, and which boxes are worth drawing at all.
They belong to the engine - pyplatypus.style - and are mirrored here so that drawing needs no Python. A test holds the two together, so the same call draws the same picture from either package.
Reach for this when you want to match a figure rather than restate it: passing colours = drawing_style()$box_colours to something else keeps one source, and typing the hex codes starts a second.
Value
A named list: agreement_colours, box_colours, class_colours, overlay_alpha, box_label_format and box_min_score.