Earlier this year I was approached by the Botanical Art Society of Australia to write an article for their newsletter's 'Which colours should I buy?' section for the Autumn 2018 edition. See the article in print here, but it's probably easier to read below. I hope that it might be helpful to anyone feeling a little daunted by the walls of colours that you are faced with in art supplies stores!
There is a lot of information and advice available on what colours you should be using as an artist, and how to mix them. I have found that working with watercolours in particular can be doubly confusing. Not only are you required to select the right colours for your needs, but also the qualities and behaviours of the individual paints should be taken into account. Is the pigment granulating, staining, transparent or opaque? You might also investigate the paint's dispersability, hiding power, refractive index, and more! It can be overwhelming.
By all means, do your research, experiment, and paint as many swatches as you like. However, if you're feeling daunted by the amount of research you could do even before picking up a brush, then do as I do: Pick a reputable brand, select a few colours you think will be useful, mix them how you like - and see what happens. Isn't that part of the fun of it after all? I find it is not even necessary to buy many (collectively expensive) colours to paint a wide array of subjects. I work from a basic colour wheel palette and have very rarely been unable to create the colour I need. As I mix all of my paints together, I therefore give little regard to their individual qualities, unless I am painting larger washes.
For many years my palette consisted of only the following:
Reds: Alizarin Crimson and Cadmium Red
Yellows: Lemon Yellow and Cadmium Yellow
Blues: Cobalt Blue, Ultramarine, Prussian Blue*
Other: Permanent Rose, Burnt Umber, Hooker’s Green Light, Hooker’s Green Dark.**
* I do not find that I really need Prussian Blue
**I probably only really need one Hooker’s Green. I almost use them interchangeably.
Today, I have introduced several more colours, although I only consider Sap Green, Winsor Blue, Yellow Ochre/Raw Sienna, Vandyke brown, Indanthrene Blue, and Winsor Violet to be ‘essential’ new additions that I use regularly.
Although there may be endless variables to consider when selecting colours as a watercolourist, it is possible to achieve professional results with a few choice colours and a bit of practise with the mixing palette.
I prefer to use tubes of paint over pans (I have nearly always used Winsor & Newton watercolours so far).
I squeeze a small amount of my paints around the edge of a ceramic plate and let the paint run into the centre for mixing when wet.
I have made myself a colour chart marking the locations of the paints on the plate should I ever need to know the name of the colour I am using.
I have one main palette that I nearly always use. I have a backup plate if I don’t want to disturb the mixes of colours I already have on my main plate, while working on a particular piece.
I rarely use swatches aside from a ‘blues’ chart I find handy sometimes. Instead, I constantly test my mixes as I paint.