When an identity arrives with a palette of nine colors, it usually means nobody could choose. We ask clients to choose, and we show them what the one color has to do before we let them pick it.
What the color is for
Links, buttons, the active state in a menu, the one figure on a page that matters, the band on a sign that says this is the way. It is a signal, not a mood. A signal color has to pass on white at text size, which rules out most of the colors people fall in love with in the first workshop. We measure the contrast in the room and darken the color in front of the client until it passes.
The grays do the work
Two grays carry every surface, rule and secondary line in the system, and they are chosen after the signal color so they neither warm nor cool it. Most of a printed page and most of a screen is gray. The signal color is the smallest part of the system and the only part anyone remembers.
When we allow a second color
When the client has two things that must never be confused: two lines of a transit network, two series of a press. Then the second color is a second signal, with its own job and its own contrast check, and still not a palette.