On
these stamps of Duttia (the 1897-8 set inscribed 'DUTTIA') and the next set (inscribed 'DATIA'), the handstamp should always be in blue. The fabulously (almost mythologically) rare earlier issues do have handstamps in other colours - Gibbons records two with
brown handstamps. (The cheaper of the two is listed a trifling £6000.)
Here, for completeness, is an example of a favour-cancelled copy of the DATIA 4 Anna, in a strip with three uncancelled copies:

Later on, you do find black controls; they're usually scarcer than the blue. Here is a pair of the last stamp of Duttia, the 1920 ½ Anna, with black controls:

Incidentally, Scott is far inferior to Gibbons for the Indian States ... in most cases. But in Duttia, for many years it listed this postal-fiscal

while Gibbons refused to do so. I gather Scott has now dropped its listing of the stamp. This is very silly: it certainly was used postally, even if my example is strictly fiscal.