I have an html page with divs that have id(s) of the form s1, s2 and so on.
As complement of this answer you can use $ to get the end matches and * to get matches anywhere in the value name.
Matches anywhere: .col-md, .left-col, .col, .tricolor, etc.
[class*="col"]
Matches at the beginning: .col-md, .col-sm-6, etc.
[class^="col-"]
Matches at the ending: .left-col, .right-col, etc.
[class$="-col"]