1. in a manner lacking color or brightness; without vivid hues
Usage: chiefly British spelling (American: colorlessly)
2. in a manner lacking interest, emotion, or personality; dully or flatly
Usage: figurative use

Examples

• The winter landscape stretched out colourlessly before us.
• She spoke colourlessly about her achievements, showing no pride or enthusiasm.
• The walls were painted colourlessly in shades of gray and beige.
• He delivered the speech colourlessly, without any emotional inflection.
• The sky hung colourlessly overhead, neither blue nor gray.
• She described the event colourlessly, as if it held no significance for her.