You have to consider the era the museum itself depicts. If it spans eras from settlement to present day, wander through the museum and see what the exhibit designer has chosen as a color motif. You may find it changes by era but there should be an overall unifying theme. It would be best to stick with the existing motif, including any iconography used, rather than try and come up with something new and different. You want the collateral to match the venue.
Edit; unless this is a school project and the museum doesn't really exist....
If it doesn't really exist, you should maybe do a web search for one that does...as I recall, Alexandria has at least
one major historical museum.