Color is 4 bytes, but we are using 4 floats in vertex data for color, which is 16 bytes.
In opengl we can specify GL_BYTE in glVertexAttribPointer and vec4 in shader and it will interpret our 4 bytes as 4 floats.
Is something like this possible in kha?

For just one color it's ok, but I want to pass color matrix to shader and using 12 (or even 20 if it should affect alpha) floats per vertex for that feels too expensive.

Ya, Kore supports that, just have to wire it up to Kha. Please create a GitHub issue.