The issue isn't with referring to colors on a chart by name but with using a color name as the sole identifier. Referring to parts of a chart by color is fine, and provides additional information, as long as a line style or shape identifier is also used, e.g., the "blue solid line" and the "orange dashed line" in the case of a line plot or the "blue circles" and the "orange squares" in the case of a scatter plot. Ideally, I think color swatches should also be included when referring to colors, so it isn't necessary to match the name to the color [1].[1] https://mpetroff.net/2019/11/figure-caption-color-indicators...
II2II|5 years ago
The use of colour swatches is interesting, though I would add that it should use a standard palette of colours to ensure that there is also differentiation based upon intensity (which would also help in the grey scale printout example).