How to fix - Samsung S5 phone colour mystery?

Hi to the experts out there.
I was fiddling with the settings of my phone, opened by tapping on the little wheel/cog button and was looking at all the different settings. I've done something which has made everything incredibly vivid, not just changed the wall paper, but all the buttons are now super bright and on the home screen the Google rectangle is now jet black rather than the usual white and when I type in it the keyboard buttons are now also black with the letters and numbers in white.
I been through everything trying to change it back, but can't solve the mystery! It's probably just one simple thing I need to do but what! Thanks.

geek_guest, Jan 4, 12:44 am

you changed you theme go back to cog and click on theme the first should be the normal one

geek_guest, Jan 4, 12:56 am

OK, went in there and fiddled but I can't get it back to how it was. It's got (in order) brightness, font, screen rotation, smart stay, screen time out, screen mode, auto adjust screen tone, day dream, LED indicator, touch light duration and increase touch sensitivity. I can't see a theme button, thought it might be under screen mode (set to adapt display) but still can't figure out how to get it back!

geek_guest, Jan 4, 1:10 am

Going to bed now, will check in here in the morning, thanks for help.

geek_guest, Jan 4, 1:11 am