Out of the blue a couple of days ago on bringing up my Win 10 desktop the background has - all by itself - changed to Windows Spotlight. How on earth could that happen. Now it is hard to find some icons (eg Fitbit and most others) because the picture on desktop "masks" /obscures them behind some of the aspects on the Spotlight picture.

So, via Personalise (right click on Desktop) I changed the background to Solid Colour. Picked out a colour (gaudy orange). Now all my icons jump out clearly. But, now on opening any options (eg NZ Herald Digital) I have a black background with text headings all in bright yellow. And that's the same for Stuff, YouTube, TradeMe etc.

What's happening? Did I do something accidentally? How can I get my selections to open up to the usual white background with ordinary black text?

All help appreciated.