First make sure you have the most up to date version of the macOS app by going to Noun Project > Check for updates.
Once updated, search for an icon and select ‘Color’ (found in the bottom, left corner of the app) to change the color from black to white. Need a different color? Select ‘Choose’ from the drop down to pick any color you want. Use the sliders, color wheel or dropper to find the perfect color. You can even paste the HEX value of any color you want. The app will remember your last few color choices which can be selected in the color drop down menu.