1200 display color problem

[AmigaMance]

The problem is a missing color. It display yellow instead of white

So, the missing color is the blue one. Have you checked the B wire of your cable if it is uninterrupted, or if the respective pin in your Amiga/monitor port is broken?

EDIT: Sorry for the confusion, the blue signal is missing not the red.

[AmigaMance]

Then, what can i do if there is no red signal in video port?

Try to isolate the problem first?..

Edit: correction applied to my previous post.