Casper header follow-up question

Hi there. I recently changed my header color so I could maintain a dark gray header while having a red subscribe button (i.e. I basically overrode my accent color in regards to the header) with the following script. However, when I open the menu in the mobile, it is still all red rather than dark gray, which looks terrible with my website logo. Is there a way to also override the color for the header menu on mobile? Thank you!

.gh-head-brand, #gh-head { background: #121212; }