The problem concerns my laptop: When filling a shape by a color in a word or excel sheet, or changing the color of the margin of the shape, the color isn't depicted on the screen. When transfering a copy of the same file to another computer and opening the file, filling color and the color of the margin both are shown.
This effect of my laptop not rendering the color first appeared a few weeks ago
Another difference I got aware of, is that when selecting a text the color indicating the selection is not blue, as it was a few weeks ago but black. I don't know whether both of these effects are interlinked.
Thanks very much for your help and advice.