"orientation" (default): per-point RGB colour derived from the local fibre direction using the standard DTI convention (left–right = red, anterior–posterior = green, superior–inferior = blue).
Metadata key: any key from @point_data or @streamline_data can be mapped to a continuous (palette) or categorical colour scale.
Fixed colour: any CSS colour name or hex string.
All streamlines in a bundle are rendered as a single scatter3d trace separated by NA break-points, keeping the widget lightweight for large bundles.
Interactive figures are produced by plotly and support pan, rotate, and zoom.