>Movie mode. This setting warms up your display, but it preserves shadow detail, skintones, and sky colors better than f.lux’s typical colors. It lasts 2½ hours, which lets you watch most feature films
Colours perceived as "warmer" (yellows, reds etc) are produced at lower wavelength and therefore by a blackbody with lower temperature (hence colour temperature). F.lux is reducing the temperature, thus producing a "warmer" hue.
>Movie mode. This setting warms up your display, but it preserves shadow detail, skintones, and sky colors better than f.lux’s typical colors. It lasts 2½ hours, which lets you watch most feature films