Copying colour accurately
Often when we go out to sketch we can return home with a book full of drawings that we hope to turn into paintings in the studio. But have we captured the colours correctly? It is tempting, especially in bad weather or if we are short of time, to just improvise our colours in a sketch. So trees are all the same green, the sky is just blue and the old wall is brown. When we come to paint from these sketches we find we don't have enough information and so have to start inventing the colours. (This in itself is not always a bad thing, and it can even help our artisitic nature to flourish!)
Here below are a few ideas that can help us to capture colours quickly and accurately when out sketching.
Use decorator's colour strips
Most decorating shops have stands with strips like these that are free to take away. Arm yourself with a selection of them when you go out to sketch, and you will have an instant reference set by which to note your colours. Just write down the paint colour or number that is nearest to the colour you see in nature, and you will have a good reference to paint from when you are back home or in the studio.
The direct comparison method
Sometimes it is useful to check your colours directly against your subject. Try these two methods:
a. Paint your colour against the edge of a piece of paper, and hold this against your subject to see how close they are (as shown here).
b. Cut or tear a hole in a piece of white paper and then use this to isolate a small area of your subject. Paint along one edge of the hole until the colour matches the subject.
Sometimes there is an element in the landscape that has a particularly special colour. Around where I live in the Lake District of the UK, there is a particular grey-green slate which is used for the walls and roof tiles of many of the old houses, and this can be hard to match accurately when back in the studio. To help you remember colours such as these, just collect a few samples, put them in your pocket and bring them back home with you.
Collect stones, bark, moss, leaves, in fact anything that you can use as a colour reference.
Painting in oils
If you are using oil paints then just hold mixed paint up on brush or palette knife and compare it with the colour in front of you. Then it is easy to adjust and re-adjust the colour until it is exactly the same as your subject.