First
Enable the post highlights for your group(s) that you want. Head over to Members>Members>Groups and enable the highlight. This can be found on the content tab.
Second
Go into your theme area which can be found within your "Edit HTML/CSS" settings in Customization>Appearance>Themes, go into your CSS Templates, click on custom.css and fill in the following code
Code:
/* The value of 4 represents the ID of the group, in this case, "Administrators" */
[data-membergroup="4"].ipsComment_highlighted:not(.ipsBox_transparent):not(.ipsModerated):not(.ipsComment_selected):not(.ipsComment_popular) {
border-color: yellow !important;
box-shadow: 0 0 5px yellow !important;
}
/* The value of 3 represents the ID of the group, in this case, "Members" */
[data-membergroup="3"].ipsComment_highlighted:not(.ipsBox_transparent):not(.ipsModerated):not(.ipsComment_selected):not(.ipsComment_popular) {
border-color: blue !important;
box-shadow: 0 0 5px cyan !important;
}
In the above examples, I've recolored the post highlights for the member group with the ID of 4 (Administrators) and 3 (Members). You can find the ID of your group at the end of the URL when you're editing your group's settings
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