Recently I download the latest release 4.2 in order to test an small application that use the gray theme.
When I switched to the ver. 4.2 I noticed some problems with the buttons on the grid panel.
Basicaly, the problem arise with mouse hover event and when I click a toggle button. The button show a violet box
instead of degrade of gray tone as occur in previous version.
The application is running without problem with the version 4.1
In order to reproduce the problem you can access to the Theme viewer example for version 4.1 and 4.2 in the following links
If you cannot wait... This is the code which must be changed either in the CSS (hex values #deb6b7 and #e1bebf) or in the SCSS of the ext-theme-gray (first line below references the Button.scss which will contain the same hex values)