PURPOSE: To obtain a picture not giving away white balance during the projection by using only a blue color for a coloring agent, which colors a cooling liquid to be sealed in the face plate front while specifying a photo transmissive rate of a coloring liquid in two ranges of specific wave length.

CONSTITUTION: A cooling liquid 5 is sealed in the front of a face plate of a cathode-ray tube 1 having a projection lens 6 and the liquid 5 is colored by a coloring agent. Only a blue color is used for the coloring agent, whereby the phototransmissive rate of the coloring agent has to satisfy the formulas I and IIwhile assuming that the phototransmissive rates (%) at the wave length 430nm, 450nm, 505nm are T430, T450 and T505 respectively. In this way, a picture not giving away white balance even when a beam current is changed can be obtained.