It takes 5 seconds for the color of the beacon beam to change when placing a colored stained glass block over a beacon.
This is an even bigger problem for slower devices (Please see MCPE-23801)
Beacons take too long to change color.
Beacon [Delay Change]
Beacons not working properly
Stained glass panes doesn't color beacons
Beacon beam disappears after going past 64 blocks.
Beacon beam looks different than before
Colored beacon beam texture stitched in y axis