The icons are documented in the Administration Guide in section 4.3.2.
126.96.36.199 Failed Inventory Connections
An entry in the Managed Computers node with an icon containing a red circle indicates a machine that failed the most recent inventory connection attempt.
188.8.131.52 Partially Successful Inventory Connections
A machine with a yellow triangle icon indicates a machine that was successfully inventoried, but one or more issues occurred while attempting to access a specific datasource or object.
Thanx for the answer. As suspected, but there are numerous reasons for each icon and there is no explanation of what (for example) failed "process" means. Also, other screens have different icons; do I need to scour each chapter for references? Is there no appendix or something with pictures and explanations?
Detailed state information on RED icons can be found on the Computer Details tab of Managed Computers, and there are five steps in the Inventory process that can result in a RED indicator. Those five steps are identified and discussed in section 184.108.40.206 of the Administration Guide.
Detailed state information on YELLOW icons is found at the bottom of the Computer Details tab of Managed Computers, and will list the specific inventory object(s) that were not accessible at the time of the inventory. Section 220.127.116.11 shows an example of a system with a YELLOW icon because the "Terminal Services" object was not accessible.