I do distinctly recall that SWT (before SWR) wanted to keep their station branding as neutral as possible. This, IMO, sets them apart from some of the "devolvable" operators (TfW, WMR etc.) who want to create their own long-term brand identity.
- WMR (part of the TfWM - Transport for West Midlands empire) was designed to be separable from the larger-scale West Midlands franchise, which is why WMTrains (the Abellio/JR East/Mitsui joint venture currently operating it) has West Midlands Railway & London Northwestern Railway as two distinct brands.
- TfW Rail (part of the Transport for Wales empire) is let by the Welsh Gov't, rather than the DfT. All that changes, branding-wise, is the operator in charge, similar to how the ScotRail franchise is run.
- Merseytravel-owned stations (irrespective of whether or not Merseyrail services call there) also have the yellow/black colour scheme throughout. Like London Overground, ScotRail, and now TfW/WMR, they seem to be keen to let concessions out rather than franchise everything.
Obviously there's no global standard for railway signs, as idealistic as that would be. SWT's blue/white running boards, in the brand-neutral "Brunel" font, seem to be the closest to following continental practice. If I recall, Southeastern's running boards are near-identical.
Southern's are also near-identical, but have a green background rather than navy blue. EMT's (well, EMR's now) are basically the inverse of SWT's (navy blue text on a white background).
All this is however distracting from the main point of the post, which makes clear that SWR think their current station running boards are perfectly adequate.