Firefox progress bar issue

[ToddAndMargo]

Hi All,

Mozilla says this is Xfce's problem.  They are just picking up
the colors from the theme

RFE: make the progress bar a different color than the background color
https://bugzilla.mozilla.org/show_bug.cgi?id=1464529

Here are some picture of the issue:

https://bugzilla.mozilla.org/attachment.cgi?id=8980791
https://bugzilla.mozilla.org/attachment.cgi?id=8981970

Are they correct?  If so, how to I fix it?

Many thanks,
-T