Perhaps this is something that comes with experience, but when starting out with watercolours, something that made the learning curve a little steeper for me was the difficulty in being able to correctly identify dried paint colours in their pans. Dark colours especially can look very similar when dry. Winsor and Newton now print colour names and pigment information on their exterior of their pans -- which helps somewhat -- but even then, this does not show when the pans are in position in the palette.
One approach might be to arrange the pan colours in specific locations in the palette, so that with regular practice it becomes instinctive as to where a particular paint is located. However, this scheme discourages the use of new and alternate colours in the course of skill development and experimentation.
My solution has been to produce "watercolour reference cards" to fit inside the paint box. This serves a couple of purposes. Firstly, the card clearly shows the position of each pan colour in relation to the others. Secondly, it acts as a (small) colour swatch, permitting decisions to be made on whether the paint is a good starting point for a desired colour.
I use a small pad of Cotman 90 lb Not paper to make my reference cards. I measure a strip to fit inside the Cotman Sketcher's Pocket Box, and then use a stencil cut from a strip of clear plastic (long sleeve shirt collar packing) to draw a number of square swatch boxes in HB pencil. (This saves the trouble of measuring and marking out the squares individually -- see the photo.) I then label each box with the paint it will contain, and then paint the swatch in each. When all the swatches are done, I cut out the strip to make the reference card and place it inside the paint box.
Even with 90 lb paper, I have found that it is possible to paint swatches on both sides of the paper. So if you are organised enough to have a couple of combinations of preferred pans, it might be only a matter of flipping over the reference card to ring the changes!
