Design mistakes happen to the best of us. See this screen shot of a blog post from a few days ago. The image the looks black and white, is actually not black and white. It is always good to remove all colour from all images, even when they appear to be black and white already.
In PowerPoint you do this in picture format - colour, see the screen shot below.
Cover image by Oleg Laptev on Unsplash
SlideMagic: a platform for magical presentations. Free student plan available.