These vector logos were made in Inkscape from existing assets in use by Auspice and nextstrain.org.
The circular tree was traced from this bitmap used in Auspice’s documentation. The resulting path was broken apart into the individual polygons and colored. The original trace document has two stacked layers: one containing the bitmap and the other containing the trace. This is handy for comparing the fidelity of the two by toggling layer visibility.
The circular tree (white background variation) has a solid white circle behind the colored polygons for use in places where internal transparency is undesired (e.g. when used on top of dark backgrounds).