I've got a 1996 Blazer LT with the 4WD and I've discovered the black ball which is mounted to the hood was missing and the intersection where the hose plugged into had a screw in it. I've seen articles like the one below. My question is, Would the light blue aqua colored hose be the same size hose I would need to connected from the reservoir to the hose intersection?

https://blazerforum.com/forum/2nd-gen-s-series-1995-2005-tech-41/under-hood-vacuum-hose-replace-95425/

 

You might have to just go for trial and error. I would think you could eye-ball it by holding up the blunt ends of several different drill bits to see which matches the OD of of the nipple (not including the barb of course).