[Solved] Calc chart not saving changes to it

[camnaval]

I am using Open Office 4.1.4 in Windows 10. I have a spreadsheet with the value of 27 items( shown in columns) in each one of 30 consecutive days( shown in rows).
Therefore each one of those cells carry a number.
I have selected an XY( scattered) chart to visualize the results.
In addition, and to better see the progress of each item during those days I use a different color and symbol for each one of them.
( Note 1: I tried using lines, but they get too tight to observe differences)
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My problem is that once I made my choice of colors and symbols for the 27 items, the program saved only a few of them, leaving most of the data with white color and therefore invisible to the eye( I could see this when I changed the background to light grey).
I have tried to modify the colors over and over again, but the program ignores all ways I know to save the changes.
( Note 2: I could not save the change in background color for the same reason.)
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Your assistance here would be highly appreciated.

[Zizi64]

I am using Open Office 4.1.4...

My problem is that once I made my choice of colors and symbols for the 27 items, the program saved only a few of them, leaving most of the data with white color and therefore invisible to the eye( I could see this when I changed the background to light grey).
I have tried to modify the colors over and over again, but the program ignores all ways I know to save the changes.

- Are you using ODF type fileformats?
- This function worked well in the previouss version of the AOO?
- Have you tried it with the LibreOffice?
- Can you upload your ODF type sample file here?

[camnaval]

Thank you Zizi64. You had the perfect answer. My files were all XLS and I never paid attention to it. When I changed them to ODF it worked like a charm.
I wish I had dared placing my question days ago. I put an unexpected number of hours trying to solve it.
Kudos on your brief and excelent reply. I wish you many happy endings like this.