Change color of dropdown toggle on homepage

Hello! I'm sorry to bother, I have tried to research and tried a bunch of different CSS classes to fix this, but I can't get it to work. When my website, myprofreshchef.com is resized smaller on a browser, and the menu becomes a dropdown toggle instead of all the menu options in the header on the home page, the dropdown toggle is in white, the same color as the background. Can you help me with a CSS class that will change that color? Thank you in advance...I really appreciate your assistance.