Elle Stone is currently among the developers for the GIMP
digital image editor software (which also has a Portable version
, if you must run software from USB instead of installed). Note that the Portable version is sometimes not the most recent one.
Her web site, Nine Degrees Below Photography
, is quite technical and primarily of interest to those who do digital photo editing. However, since the introduction of GIMP version 2.10 awhile back, the program's capabilities have become much more useful to those who do non-digital art (such as painting with actual paint). This is because the program allows you to express color in formats that are more consistent with the way that color is described in painter-friendly locations such as handprint
: hue, value, and chroma.
In particular, this page
might be of interest to painters. Just keep in mind that "painting" is a term used in digital art, as well as paint tubes! Likewise, "mixing" is done differently in digital and in actual paint. Nevertheless, the info is useful, especially for those who have never thought about these things.
As Elle notes on the above page, the color rendition of a computer can vary widely, depending on its technology and whether or not it has been profiled and calibrated. Almost certainly your own computer, whether desktop of handheld, has not been profiled and calibrated (you would know it).