Colour for Pricing

I was thinking about the way places like Yo!Sushi use colour to indicate price (dishes on different coloured plates cost different amounts and then the waiter counts up your empty plates at the end) and I thought how good it would be if the colour was used as an indicator of the total as you went along.

So I imagined a system where, for example, you enter into a computer the amount you would like to spend at the beginning of the meal and then as you order dishes the computer keeps a running total and the colour of your booth/table/place mat turns from one colour to another (through illumination) so you are automatically aware of how much money you are spending.

This would be a good thing for the customer but perhaps the bill awareness would not encourage restaurants to install this system! Perhaps it could be used to indicate time spent so it would encourage visitors with time restrictions. 

In terms of indicating the course of a set period of time, this could be used in other settings too such as a meeting room, gym, etc to avoid people having to keep looking at their watches.

Eg: a meeting is scheduled to last for 2 hours so the computer is programmed to change the colour of the ceiling from blue to green in the 1st hour and green to yellow in the 2nd hour. This way everyone has a clear consciousness of the passing of time and so schedules can be kept to more easily.