Unofficial builds (security updates):
KCAL - Advanced color control (supported by default since 29.03.2018)
/sys/devices/platform/kcal_ctrl.0/kcal - (0-256 0-256 0-256) - Controls R/G/B Multipliers
/sys/devices/platform/kcal_ctrl.0/kcal_min - (0-256) - Controls minimum RGB Multiplier value
/sys/devices/platform/kcal_ctrl.0/kcal_enable - (0-1) - Enables/Disables RGB Multiplier Control
/sys/devices/platform/kcal_ctrl.0/kcal_invert - (0-1) - Enables/Disables Display Inversion Mode
/sys/devices/platform/kcal_ctrl.0/kcal_sat - (224-383 or 128) - Controls saturation intensity - use 128 for grayscale mode
/sys/devices/platform/kcal_ctrl.0/kcal_hue - (0-1536) - Controls display hue - may have issues with msm8x26 in the higher values
/sys/devices/platform/kcal_ctrl.0/kcal_val - (128-383) - Controls display value
/sys/devices/platform/kcal_ctrl.0/kcal_cont - (128-383) - Controls display contrast