It's the background image of your first section, the second image is in third section. You can simply replace them by inspecting your sections in cornerstone builder and change the background image there
Please check this https://theme.co/apex/forum/t/cornerstone-interface-inspector/124
Please note that you have to switch back to background image to replace it since you said, your current background is color. You can only replace it by switching back to the background image.
And there is no Callout color option available, you can only change them through CSS. Which part do you wish to change the color? Maybe I could provide a simple CSS
And add this CSS to your global custom CSS to change your header background color,
background: #ccc !important;