Hi,

I'm glad to hear that you like Ornatrix so far. 

You don't need to convert the hairs to mesh to texture it. By default, the hairs will inherit the UVs of the distribution mesh/scalp/character. Paint the textures on the character and assign them to the hair shader.

This video shows how to color the hair along the strands. 

Here you can see how to paint vertex colors on the strands. This is only supported by Arnold at the moment. 

And some extra info about shading in the documentation. 

All those examples are for Redshift, you may need to find equivalent nodes for other supported renderers. 

1- easiest way to overall colour the hair using the underyling geo. Does it work not only textures and uvs, but also vertex colors?

It supports texturing using the underlying geometry and per-vertex colors in Arnold. 

2- additionally to that, if id like to use per strand uv, i guess then the multiple uv tags would be needed. Again, i cant seem to put them visible at all.

Per-Strand UVs just generates a separate UV island for each strand, not separate UV tags.

1- i tried using the "export polygon" to make a collapsed copy, and the uv tags show up. It's, however, impossible to copy them to the Ornatrix object. They disappear instantly, only if i disable the mesh from strands op, but then it doesnt take into account the multiple uv tags.

As you noticed, it has to be exported to get the actual mesh hair and the UVs. When Mesh from Strands is still on the hair object, the mesh there is not final, it is still a hair object, so you can to export it to get the final mesh. If I remember correctly , C4D doesn't support multiple outputs from a single modifier stack. That is why it works this way.

2- however, there is some internal naming of the uv tags (ie -"channel2"), so even if the tags dont show up, i can still access them using their names, so it's a workaround.

So, if you delete or disable Mesh from Strands after exporting the mesh, the UVs remain in the scene somewhere and you can still access them?

Jeordanis Figuereo (Product Designer. EPHERE Inc.)