The command line tool pastel appears to be a brilliant CLI to work with colours in the command line.
For some reason, I find myself wanting to mix colours together quite frequently, for example, and I can do this with pastel:
pastel mix f8f8f2 darkblue | pastel format rgb
# rgb(148, 122, 192)
The reason I'm piping pastel mix into pastel format is because the output of pastel mix is actually more complete:
