In the dashboard the orange color is used for the "Hosts with no reports" status group, and in the Hosts page, indeed, hosts that have been powered off are listed with an orange icon.
But inside the orange icon there is a "S", and when hovering on it with the mouse pointer a popup appears telling "Out of sync".
"Out of sync Hosts" is a different group in the dashboard, and it should be listed in light blue color! Actually, also the pie chart shows those hosts as being out of sync.

See attached sample.

So... is a powered off host a "host with no report" or an "out of sync host"?
In the first case, orange should be used everywhere, and the popup (and maybe the icon, too?) should be fixed.
In the second case, light blue should be used everywhere.

I'm new to Foreman so I might be missing something, but I can guarantee this looks very confusing for a newbie.