Happily browsing British Library manuscripts today, and found Yates Thompson 49, a 15th c French book called 'La Legende Doree' (the golden legend).
What's striking about book 2 is that the miniatures are unfinished, giving you a view into the processes of the minaturist - this is vol 2, f 27v about St felix being pope.
In this image and several others, the sketching out is done, and the blue has been blocked in, and a dark gray shade - don't know if this was the intended finished colour, or a base for something else.
What's similarly neat to see is that the initials are done and totally finished - meaning that the miniaturist (doing illustrations) and the rubricator (doing initials) are likely two different artists - on top of the calligrapher. Not certain if the person applying the gold to the initials is different from the person who paints them in with colour and details.
Do have a flip through the other images to see more examples.