title: How to change fixed button to change BG color if its scrolled over sections that has same color?
body: <p>Basically, i have fixed button on bottom that scrolls over the page on mobile. The color of button is yellow and i want when the button scrolls over sections that are same color as button, to get additional class or change style directly inline and set BG color to white.
  Is it possible with Observer or something similar?
  Thanks!</p>