The red and blue are the adjustable ones in this model, if I recall
correctly.

Comon causes for the fault you have, are a failure in the video drive
circuits, or the CRT is defective. More often, it is the CRT that goes
in these monitors.

A tech who is properly trained in monitor service, and has the tools to
work with, can check the monitor for you, and tell you what the fault
is.

Jerry G.
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