5a693e87_Plus__known_issues____RealVNC___Workaround
[ID] 133 [Description] The line speed estimate may be incorrectly displayed as 0 kbps, preventing VNC Viewer Plus detecting a fast network and automatically enabling full-color mode. [Status] Under consideration. [Workaround] 
Use the compression/quality slider on the Display tab of the VNC Viewer Plus Options dialog.
VNC® Viewer Plus (known issues) - RealVNC®
Workaround