Pdf image background looses colour

I am writing a manual complete with small screenshots in “Write”.
The background behind the black text in these screenshots is a plain mid-grey (so there is no black border around each image)
If I export document as PDF, the images loose the grey background and appear white. This gives the pages an untidy appearance as the text in the images can be confused with the main body of the written text.
If I print a page from the original odt file the images have correct appearance.
If I use Cute PDF to create PDF then grey background is supported (unfortunately my contents page hyperlinks are not)
I have tried all permutations of lossless format settings within the Export PDF dialogue box.
Is there a fix for this?
Thanks in advance.

Fixed it!
Examine properties pane when image is clicked.
In ‘Image’ section look at ‘color mode’.
My images said ‘default’. Changed this to ‘Grayscale’ and now they all convert correctly in PDF.
It is strange that importing a bitmap does not work without this fiddle. Maybe a function of the image source.

Would rather say that this is a work around. Word processors since long are What-You-Is-What-You-Get. When the “default” colour mode of an inserted graphics outputs as a black box in the printed (pdf) output, then I want to see it also displayed as black when I edit the document in Writer.

Changing Color mode to Grayscale changes the image to grayscale, but I want it in color obviously!

There are three open LO bugs possibly related to this issue.

One of them mentions the same workaround as “El cid” mentioned. Best is to report in one of them that comes closest to your experience or alternatively post a new bug report.