Zenith with jaundice

[wa2ise]

There should be inside trimpots for adjusting individually the red contrast and brightness (gain, bias), for green and for blue. Sounds like the blue is a little low. The cathodes inside the CRT probably have aged some. You can either turn up the blue or turn down both green and red. Adjust the biases so the blacks look grey (this is with the user brightness control turned up higer than normal), and then adjust the gains so whites look white and not color tinted.