This is, I think, finished.
It certainly was a task and I needed to persevere at the beginning. I was really hesitant about adding colour and seriously disliking the colour as I started to add it. The more I did, the more comfortable I became with adding colour.
I think what helped with the colours was the use of a limited colour palette. Indigo, prussian blue, gold ochre, burnt sienna and bronze green made the basic palette up. Mixing the colours gave me plenty of variation in colours and tones while at the same time keeping a coherence.
I started adding shading with a biro. As this drawing was a testing ground for various ideas, I used a cool grey Pitt Artist pen to add the rest of the shadows. I found the result pleasing, particularly after adding colour. A darker grey may have worked more to my tastes of high contrast, but this is a starting point.
Indeed, I rather like the combination of biro and pitt pens. I did end up adding some cross hatching to some areas to intensify the dark areas betwixt the elements of the design. That darkness helped to lift the colours somewhat.
To add highlights, a white Sakura Soufflé pen was used. I also had a hankering to add some metallic highlights too, so a gold metallic Gelly Roll came in useful.
Using flat colour washes and letting the grey shadows add volume seems to have worked well enough. I may, later, try out some coloured pencils to add more shadowing. But not until after breakfast!