Dashboard graph consistency

I have two dashboards set up with graphs, the only difference between the two of them is that the filters are ‘this week’ and ‘last week’. As the information on both of them relates to members of staff, it would be good if the colours that represent the people remained the same for both sets of data, but they dont. It would be nice to be able to compare and contrast at a glance, rather than having to check the key at the bottom… I think at the moment it just displays them in order of who works on the system first.