Microsoft PowerPoint offers several simple color adjustment options that allow you to quickly and easily format the pictures in your PowerPoint presentation. If you're creating an art masterpiece or just want to customize a document to fit the printer's settings, you can convert your images to black and white in PowerPoint
How to change an image in Microsoft PowerPoint in black and white
Black and white image in Microsoft PowerPoint is easy! The color setting only affects the image inserted into your document (and is reversible). It has no effect on the original file.
First, click on the image in your document.
On the Ribbon, go to the Format tab.
 Click the "Color" button.
In the drop-down menu that appears, click the Saturation 0% option in the Color Saturation group.
 Voila! Your picture is now black and white.
And do not worry. PowerPoint still has the original image with all the embedded colors, so you can easily access (or even change) the original colors. To return your now black and white image to its original state, just click the Format tab again and click the Reset Image button.
And just like that, your picture is back in the original color.