PURPOSE: To reduce the upset of hue balance and improve color display accuracy by inputting gain signal and sea clutter suppressing (STC) signal to a level shift circuit from another signal system for the gain control of reference original signal.

CONSTITUTION: Video signals SVD are formed with the operation of a radar and applied to comparators 12A, 12B and 12C constituting color discriminating means 12. On the other hand, gain signal and STC signal are inputted to a level shift circuit 10 as level adjusting signals. Based thereon, the circuit 10 gives reference original signal VR a slope corresponding to the sea clutter component of the video signal. Based on the reference original signal given with the slope, a plurality of different level hue reference signals VR1, VR2 and VR3 are formed and gain signal G is added to the reference levels of the whole a plurality of hue reference signals VR1, VR2 and VR3. Thus, differences between the hue reference signals VR1, VR2 and VR3 are held constant and, at the same time, the levels of the whole reference values are controlled to a suitable magnitude for the video signals SVD.