What makes a colour palette feel 'calm' and trustworthy?

Some interfaces feel restful; others feel loud and stressful. A lot of that is colour. Why?

A few principles:

• Restrained palettes (one main colour, a neutral range, one accent) feel calmer than rainbow UIs.
• Cooler, muted tones often read as trustworthy and professional.
• Reserve bright accents for the single most important action, so they keep their power.
• Never rely on colour alone to carry meaning — add icons or labels for accessibility.

What palettes feel trustworthy to you? Share examples and we'll discuss what makes them work.