xcolor should accept spaces and periods in color names (at least)

[xworld21]

Beamer color names include spaces and periods (e.g. alerted text.fg). This won't be accepted by the xcolor binding because the regex is too restrictive:

LaTeXML/lib/LaTeXML/Package/xcolor.sty.ltxml

Lines 263 to 264 in 1301850

	my $name_re = qr/|[-]*\.|[-]*[a-zA-Z0-9@\*_]+|[a-zA-Z0-9@\*\-_]+/;
	my $ne_name_re = qr/[-]*\.|[-]*[a-zA-Z0-9@\*_]+|[a-zA-Z0-9@\*\-_]+/;