The darktable manual says:
- up to demosaic – Image is in raw data format with only latent colors
- between demosaic and input color profile – Image is in RGB format within the color space of the specific camera or input file.
- between input color profile and output color profile – Image is in Lab format.
- after output color profile – Image is in RGB format as defined by the selected display or output ICC profile.
Also, it talks about two profile conversion steps (rather than an assignment and a conversion): “This process implies that the pixelpipe has two color conversion steps: input color profile and output color profile.”