[old_tv_nut]

I assume this chassis has separate red, green and blue video output transistors driving the cathodes. Then, that kind of smear indicates the video output transistor for the blue cathode is saturated (drawing max current and producing minimum voltage). A possible fix is to adjust the G2 voltage (making the picture darker) and then turn up the brightness (making the video output transistor collector voltages higher and avoiding saturation).

[Hope I didn't get that backwards - having the service info / setup procedure would help.]