IPAM takes the settings from Orion for effecting changes in IPAM settings page.
Orion settings page’s look and feel are managed in C:\inetpub\SolarWinds\Orion\styles\Admin.css as mentioned in thwack.
IPAM takes inputs from above to effect changes in IPAM Settings page.
The path C:\Inetpub\SolarWinds\Orion\IPAM\Admin will contain a file Admin.Overview.aspx.
This aspx contains a line which reads IPAMmaster:CssBlock Requires="~/Orion/styles/Admin.css,~/Orion/styles/Breadcrumb.css" runat="server">
effecting changes in Admin.css should work for IPAM too.