Poor colour choice for update button

[maddisondesigns]

Describe the bug
When clicking the Update button on a Page/Post, it changes to white text on a white button with a white gradient, and becomes totally unreadable.

To reproduce
Steps to reproduce the behavior:

1. Edit a page
2. Click the update button

Expected behavior
Buttons should be readable at all times, including when disabled or during an update process

Desktop (please complete the following information):

• OS: macOS 10.14.3
• Browser: Firefox Quantum 66.0.2
• Version: 5.2-RC1-45273

[sarahmonster]

This seems to be a duplicate of #15029, which I apparently assigned to myself and then promptly ignored. ;)

[jemlovestodraw]

Agreed, it is hard to read. A simple fix could be to put the text (Updating...) in the medium blue of the original button.

[aduth]

Closing as duplicate of #15029. This is a regression.

[aduth]

Duplicate of #15029