Change header colour to box colour

.sticky-disabled .tc-header{
      background-color: #fff;
}

That should do the trick.

Actually change the hexadecimal code to be #F5F5F5 that is actually closer for you. Always change the hexadecimal value to change the color of the header background as you wish.

Now for cross browser support you may need:

-moz-background-color: #fff;
 -ms-background-color: #fff;
 -o-background-color: #fff;
 -webkit-background-color: #fff;

That shoudl support most browsers just to be safe.

Do you mean replace the black background? (I can’t see any grey?)

Try

.tc-header {
    background-color: #fafafa; /* Change color if needed */
}

Sorry, I see what you want:

body {
    color: #777;
}

Only the Headers, change to:

h2 {
    color: #777;
}

If that is too generic (ie changes all h2’s) then say which headers you want.