Q: I have icons displaying over my server and scopes in DHCP Manager. What do they mean?
A: The Microsoft TechNet article "DHCP Console Icons Reference" provides a good explanation of the different overlay icons that can be present in DHCP Manager. This article shows the overlay icons for servers, scopes, options, and leases.
You can also check the event log for additional information about possible problems. In general, a blue circle with exclamation mark means all IP addresses in a scope have been allocated, and a yellow triangle with an exclamation mark means 90 percent of all IP addresses in a scope have been allocated. These are the most common icons I've seen.