I thought I'd share my latest homework with you. ; )
In the left picture you can see that I placed a healthy brushstroke of every colour on my palette, fresh out of the tube, and put them down the centre of the page. Then, using ultramarine blue, burnt umber and white, I made greys to match the exact value of the colour. I got the first two wrong. Doh. But then I got the hang of it.
The picture on the right is a black and white photo of the same page. You can see I got most of my values right. (Phew).
I learned that tube colours are a lot darker than I thought. Also, intensity, like the hot opera pink, is very misleading.
I did this exercise years ago and my repeating the exercise yesterday was long overdue. Very helpful!