Thank you, tuanphan! That worked perfectly. Do you know how I could make the font color change on the button to either Gold rgb - 166, 121, 069, hex - #A67945, or Teal rgb - 036, 081, 082, hex - #245152?
I tried:
header#header [href*="calendly.com"] {
background: white;
color: #245152;
}
But it didn't change it.