CRT TV with blue centre and green edges?

PAL flat screen CRT. The colours vary according to the programme, but between channels the centre of the picture is blue (as I think it should be) and the edges are bright green. I have switched it on and off several times at main switch, but it makes no difference. There is no clunking noise when I turn it on. TV usually on standby without being switchewd off at mains. The colours seem to depend on the signal, so the edges can go magenta if the programme material is bright.