panelTitle is the one which is changing color of Details, features, changelog labels in extensions panel . Let me know if this is what you looking for.

Modifications in settings.json :

"workbench.colorCustomizations": {
"editorGroupHeader.foreground": "#f40808",  
"textLink.foreground": "#f40808",          
"editor.foreground": "#f40808",             
"panelTitle.inactiveForeground": "#f40808",
"panelTitle.activeForeground":"#f40808"

}

and got this result :

You can refer to this for further information : https://code.visualstudio.com/api/references/theme-color