What enemy threat colours mean
The nameplate should answer the first question in a fight: how dangerous is this opponent?

Colour is a warning
Green indicates an opponent at or below the character’s threat range. Yellow and orange warn of increasingly difficult fights. Red marks a major mismatch. Elites and bosses carry extra threat, so level alone does not describe every encounter.
A large gap changes the fight
The combat rules reduce outgoing damage and increase incoming danger when the opponent is much higher level. At a large gap, the combined damage of attacks, spells, damage over time and summons is also controlled. Splitting an attack into many small hits does not remove that protection.
Trying is still possible
The game does not forbid an attempt merely because the target is red. Positioning, equipment and training remain relevant. The purpose of the warning is to make the risk legible, not to promise that every red target can be defeated with the same routine.
Why the whole group matters
A warning colour describes an opponent, not a guarantee about the surrounding room. Several individually manageable creatures can attack together, especially when movement draws in nearby enemies. Before judging a build by its first successful kill, watch whether the next target brings a group into the fight. The extra damage and reduced room to retreat may change the result.
A practical reading order
Read the displayed level, then the elite or boss label, then the space around the target. For ranged vocations, a clear retreat matters; for melee, a valid approach matters. If a higher-level target takes a long time to kill while exhausting supplies, the warning is doing its job. Returning after an equipment, training or level improvement remains a valid route forward.