Burnt Sienna 88% + Warm Blue (Ultramarine) 12%
Earth mix. Start with Burnt Sienna, then steer slowly with Ultramarine. Stop early.
Adjustments:
Warmer → add more Burnt Sienna
Cooler / darker → add a touch more Ultramarine
Lighter value → dilute
Deeper value → glaze
Fix it fast:
Too bright → add a pinhead of the opposite (Cool Blue / Phthalo Blue)
Too muddy → add more of the base colour to clean it
Wrong hue → nudge with the steering colour