In an electronic PDF, cross-references will be hyperlinks that take the reader to the target. Color is used to make them visible, in addition to whatever indication a PDF viewer will provide on hover. The parameter latex.pageref is by default no in this case, but may be set to yes to include the page number of the target in the cross-reference.
In a print PDF, cross-references will not be active hyperlinks and will be the same color as the adjoining text. The parameter latex.pageref is by default yes in this case, but may be set to no to not include the page number of the target in the cross-reference.