A color scale is a group of colors that work particularly well together. This harmony of colors can be seen in shades of one color that are produced by the juxtaposition and blending of similar and related tints.
The colors produced from the primary colors yellow and blue form the cold range of colors. However other colors may also be added to the color scale, provided they do not start to dominate, but link into a harmonious common theme. For example, if a little red is added to a blue tint, violet is produced.
The warm colors include various red and yellow tones, and the color blends obtained from them. Again, it is also possible to add colors from other scales, such as a little blue, in order to diversify the warm tones.
Broken colors are the dull, brownish-gray tones obtained from mixing together two secondary colors or a secondary color with a primary color. This color scale can be both warm or cold.
Your illustrations will appear particularly harmonious and natural if the colors are repeated, either in the colors of the various elements of the image or within the colors you are using themselves. For example, if I’m painting a red apple with a green leaf, I might add a little green to the red of the apple and vice versa so that the colors work better together and appear to be linked.