Fixed Color Scheme

Hi,

I have a bar chart that shows the occupancy of different rooms by date.

I have two problems with this:

1. the diagram should have different maximum values for each individual room
   for example:
   Room A: 11 places
   Room B: 20 seats
   Room C: 4 seats
   There should be a fixed maximum number for each room and thus different color scales per room.
2. however, the data colors change after the highest value specified for the selected room.
   (see photos).
   How can I make the maximum value "fixed"?

Which settings do I have to make?

Thanks!