With Color/BW (ICR), when switching from a color screen to black and white, the IR cut filter is removed to widen the band of light that enters the image sensor, increasing the amount of light and improving sensitivity.
With Day/Night (Electrical), the IR cut filter is left in place but the screen is electrically switched to black and white, and the sensitivity can be increased by increasing the gain, but compared to the Color/BW (ICR) format, the effect is less and noise is more noticeable.

ICR：Infrared Cut-filter