Your symptoms sound like a malfunctioning pincushion amplifier. What it
does is partially AM modulate the horizontal deflection sawtooth signal
with some the vertical deflection signal. Factory adjustment of the
amount of this modulation is made to reduce/eliminate barrel/pincushion
distortions on the screen. Since your symptoms are a pincushion
distortion that gets worse as the monitor warms up, this suggests that the
modulation level changes to an out-of-spec condition with increasing
temperaure.
The reason for this AM modulation of the horizontal sweep amplitude is
that, because of geometric effects related to the path of the electron
beam, it takes a somewhat different amount of horizontal deflection
current in the deflection yoke to horizontally deflect the beam by a
given amount on a flat screen when the beam is near the vertical center
of the screen than when it is near the top or bottom of the screen.
The blue shadowing effect sounds like a severe misconvergence problem.
Since the circuits that control the dynamic convergence compensation
also deal with the pincushion/barrel distortion correction level, it
looks like that is where your problem is.