Problem with Bryston 4B SST.

@newebie1963-

     As luxman said: normal

     ie: Look at Page 2, number 2, under ’LED Indicators’ and then, immediately below: ’Power up sequence’, in the manual:

                    http://old.bryston.com/PDF/Manuals/3B_4BSST_MANUAL.pdf 

Thank you. Never noticed this before, must be my dementia. 

     All you'd have to do is take your eyes off the amp, for a couple seconds,  after switching it on. 

     Dementia's my story.

     You're probably too young for that crap!

I've heard great things about that amp. How does it perform?

I have the exact same amp. It is the correct behavior. This is from page 2 of your manual:2. L·E·D INDICATORS
Each SST2 channel has a LED indicator to monitor the following conditions:
Unlit - indicates channel has no power.
Red - indicates channel is muted (power-up)
Green - indicates channel operation is normal.
Flashing Red - indicates channel clipping.
Orange - indicates channel thermal shutdown.
POWER UP SEQUENCE
After pushing the power switch ( in the picture above), each channel LED will turn from unlit to red (mute). When the power supplies have stabilized the channel will come out of mute and the LED will change to green (normal operation).
UNLIT L·E·D ( No power )
The SST2 channel LED when unlit indicates no A/C mains power is present at the channel. If both channel LED indicators are unlit the amplifier probably needs only to be powered on.
CLIPPING ( flashing red )
Clipping occurs when the channel output level no longer can follow the level increase at the input (Over driven input condition). When an SST2 channel is driven into clipping the channel LED will change from green to red then back to green when the level is reduced ( Flashing Red ). Momentary clipping can be tolerated, however it indicates that maximum undistorted power has been surpassed and potential speaker damage may result if overload conditions persist. Any amplifier that is constantly operated into clipping indicates a more powerful amplifier is needed for that application.
THERMAL SHUTDOWN ( orange )
Each channel has thermal shutdown circuitry to prevent damage due to overheating. Should thermal shutdown occur, the channel will mute, and the channel LED will turn orange indicating this condition. When the channel has cooled to a safe operating condition the channel will return to normal operation. Persistent Thermal shutdown indicates steps need to be taken to increase airflow across the channel or channels heat sink. ( Also see installation section on ventilation ).