It appears to be impossible to change the color of the font used for the date/time field on the Master slide. I have tried several different approaches and none of them have any effect.
Hello Alex, Thank you for reporting the bug. Please attach a sample document, as this makes it easier for us to verify the bug. I have set the bug's status to 'NEEDINFO'. Please change it back to 'UNCONFIRMED' once the requested document is provided. (Please note that the attachment will be public, remove any sensitive information before attaching it. See https://wiki.documentfoundation.org/QA/FAQ#How_can_I_eliminate_confidential_data_from_a_sample_document.3F for help on how to do so.)
Created attachment 112658 [details] example showing problem
Attached example presentation. Either there is an undocumented way to do this, or it is a bug.
Select View/Master/Slide master. Resolved as notabug, please if you are not agree reopen it.
That's exactly what I did. I opened the View/Master/Slide master, then,as I said, any attempt to select the date/time field and change the color has no effect.
Created attachment 112817 [details] Screenshot I can edit without problem, please see the attached screenshot.
OK, and I assume it actually changed the color in normal view? Your screenshot shows what I try to do, and it just doesn't work.
Created attachment 112914 [details] field unselected This shows the date/time field before attempting to select it.
Created attachment 112915 [details] Partially selected Apparently selected - but actually not. If you click on the date/time field the background goes gray so you think you have selected and attempt to change the properties. Aha got you. You haven't really selected it and any attempt to change it has NO EFFECT. Cue several days of frustration.
Created attachment 112916 [details] REALLY selected Now you did - well done. What you realised was if you double click, or maybe even triple click the background now goes black. Now you really have selected it and any changes you make really will make a difference. Well done, you've earned yourself a coffee.
So, please see attachments. It turns out the problem is not that the colour can not be changed, but that it is not at all easy to actually select the date/time field, and in addition there is an intermediate stage where it appears you have selected it, but you haven't. I still think this rates as a bug, or failing that a lack of documentation, but I am closing the bug. Hopefully this bugzilla report will help others struggling like I have for several days, should they manage to find it.