I have HP gear from the 70's through the 90's with badges. The blue and black badge tends to be from the earlier decades and the monochrome one from the later ones. So, yes, the monochrome one is often newer, but there's a significant overlap in the overall chronology (i.e., there doesn't seem to have been a global switch from one badge style to the next). For a particular device model, though, it's probably OK to use the generalization.
Prior to the 70's everything I have has the logo either printed on or etched/engraved/stamped into the panel.