Just FYI for devs.
Have two rigs, both Win7ProSP1, both using the same skin (slightly modified Primavera by essorant), both using Firefox 50.1.0 with same theme and plugins.
One rig still has WB 10.46 beta, the other WB10.5.
The rendering of tab text in FF changed with 10.5 - rendered in white in 10.46 beta, in black in 10.5.
All the best & Happy New Year!