Can I have a perfectly smooth pigmented stucco with even colour?

There will always be some tonal variation across the surface. This occurs as the trowel edge runs across the surface and it slightly separates the pigment from the cement particles leaving two slightly different colours. But it does give the look and feel of a natural finish. If you want to avoid colour variation, it is necessary to scrape the surface to remove the laitance (*) from the surface, although this will result in the surface having a slight texture. (*Laitance – the fatty particles which float to the surface of a plaster when it is trowelled up.)