Having difficulty with Impress Template

I can’t seem to figure out how to make a LibreOffice Impress template that works.

I create the template and using the master slide feature set the background color that I want for all slides. I then set the text and bullet points to the font color white. So basically I have one background color for all slides and one font color (white) for all text and bullets.

But when I try to use the template the font and bullets are black and sometimes the background color randomly changes to white.

I am saving my presentations at .pptx for broader compatibility.

What am I doing wrong? Is there a step by step guide to doing this right?

With what?

How to open files from MS-Office 2007 or 2010 (.DOCX, .XLSX,…)?

I’m not sure what you mean? I save them using LibreOffice Impress

Well, if you work with LibreOffice, you should save in the native file format ODP.
If you save in Impress in the alien format, you may have compatibility problems.
So it’s the other way around than you think.