Chances are the vision mixer in Maidstone likes a less transparent logo than the vision mixer in Southampton. If the logo is added on the vision mixer desk (which is quite likely) then the transparency can easily be altered by a control on the desk (or a preset memory setting)
If the logos are added after the vision mixer, then it could be the bits of kit in Southampton and Maidstone have different capabilities (and the one in Maidstone is not capable of the same effects)