d = new Date();

document.write("<style type=\"text/css\">@import url(");
// Month is 0-based:
if(d.getMonth() == 11) // December.
	document.write("colors-xmas.css");
else if(d.getMonth() == 9 || (d.getMonth() == 10 && d.getDate() < 10)) // October through November 10.
	document.write("colors-fall.css");
else if(d.getMonth() == 6 && d.getDate() >= 0 && d.getDate() <= 5) // July 1-6
	document.write("colors-july4.css");
else
	document.write("colors.css");
document.write(");</style>");