You really need to improve your search fu. See: http://search.cpan.org/~jmcnamara/Excel-Writer-XLSX-0.05/lib/Excel/Writer/XLSX.pm (found by a search engine with a query of "perl EXCEL::WRITER::XLSX".

Near the bottom of that exceptionally comprehensive documentation page:

set_bg_color()

which also appears in the index.

So, please, skip the excuse you offered last time I mentioned your need to search more effectively:

• "There you go again with the lazy questions!"

  "See also Re: week of the year... and your subsequent promise to read the docs before asking a question like the parent SOPW."

• Re^2: Re^2: trailing zeroes with EXCEL::Writer::XLSX
  by fionbarr on Aug 11, 2014 at 10:37 EDT
   
  "I do research my questions before I post them; if I do not find an answer am I precluded from posting the question? I am not trying to offend those to whom the answer is easy."

RTFM! That's advice I usually avoid, because it's seen as unkind to noobies... but you're not a newbie.