I am trying to add a white logo to the merged header on homepage only, and I have been trying to upload a white logo to page header plugin to replace the logo over and over again, also I can see the url of logo which has been added the page by developer tool. but cannot be displayed. you can see the code below <img class="header-image" alt="海外寄宿网" src="https://mysite.com/wp-content/uploads/2018/07/hijisu-logo-white.png" title="海外寄宿网" srcset="https://mysite.com/wp-content/uploads/2018/07/hijisu-logo-white.png 1x, https://mysite.com/wp-content/uploads/2018/07/hijisu-logo.png 2x" width="177" height="50">
unfortunately with GP 1.6 page headers, it only swaps the standard logo, so if you are using a retina logo in your customiser it defaults to that, hence the white logo is not displaying.
GP 1.7 should be released within the next week. Which has a new Elements module that adds this option to page headers.
Alternatively i would suggest you use an SVG logo instead of the PNG, then you won’t require the Retina logo. Let me know.