Anyway, yesterday I decided to do the color chart on the paper I am currently working with (The Langton 300gsm rough). I had an old chart as well, but that was done on a cheap sketchbook paper which toned down and muddied the colors. This made it impossible to get a realistic idea of how they looked like on a good watercolor paper.
When the chart was ready, I was in for a double surprise. Not only the colors were bright and clean, but as a bonus the granulation didn't look as obvious as I remembered from my previous trial. So now I am thinking to give the Inktense another try (maybe not with people's faces though).
And here is the color chart - quite basic, but it's all I need for now: