What is this blue/green switch for?

[bongo_fodder]

I was working under the steering column (in the pic that is the break peddle going off to the bottom right) and saw this switch with Blue/Green labels and a min<->max dial:

The wire behind it seems to go around to the left and disappears into the centre area under the automatic gear selector (I guess the engine bay).

I briefly turned it on/off - I didn't notice anything happening

[WestyK]

I assume you have aftermarket white dials.
I have seen these used to adjust the back light colour and brightness.

[g8dhe]

Turn your dashboard lights on then use the control it will change the colour and brightness of the backlighting. Its an after market addon https://visual-performance.co.uk/mazda-bongo-200-c.asp