Concat of two html file

By launching two SQL scripts I get two html files report_1.html and report_2.html with different background and text colors (white/blue for the former and silver/black for the latter) but if I try to concat the two html by using the CAT function on UNIX Server where Oracle is installed (cat report_1.html report_2.html > report.html), I get a new html file where the two spools have got the colors of the first spool that is white/blue. I'd like to get a new html file with the two lists of data in different colors.
Can you help me?

Thanks!

Double post, continued here, thread closed.