Excel allows the colour of header and footer text to be 
specified. A header displaying "test test test" with the
middle "test" in red will be stored as follows:
test &KFF0000test&K01+000 test

org.apache.poi.hssf.usermodel.HeaderFooter.stripFields() removes 
formatting tags from headers and footers, but this is missed.

This patch removes these colour formatting tags by adding the 
following new regexes after the existing ones
        text = text.replaceAll("\\&K[\\dA-F]{6}", "");
        text = text.replaceAll("\\&K[\\d]{2}[+][\\d]{3}", "");

An example of an Excel file with this an other formatting is 
used for a unit test