If you really want to use single quotes in the outermost layer, remember that you can glue both kinds of quotation. Example:

alias rxvt='urxvt -fg '"'"'#111111'"'"' -bg '"'"'#111111'"'"
 #                     ^^^^^       ^^^^^     ^^^^^       ^^^^
 #                     12345       12345     12345       1234

Explanation of how '"'"' is interpreted as just ':

  1. ' End first quotation which uses single quotes.
  2. " Start second quotation, using double-quotes.
  3. ' Quoted character.
  4. " End second quotation, using double-quotes.
  5. ' Start third quotation, using single quotes.

If you do not place any whitespaces between (1) and (2), or between (4) and (5), the shell will interpret that string as a one long word.