I focus on primarily making barrels since everything else is a waste of time till the weapons are orange, and at like 2/3/4 I got blue versions of the barrels that also required investigation parts. However I'm up to level 10 now and haven't gotten a blue since, so my investigation skill is kind of just sitting around 30 atm since I don't need it while my research and armsment are in the 160-190 range both. Is making the blue schematics just like... a random chance thing?

If you reverse engineer the barrels you are making there is a chance to learn the higher version of said pattern,

 

for instance, i do artificing, i reverse engineered Resolve Hilt 9 till i got the blue pattern, then RE'd the blue ones till i got the purple pattern.

 

 

Thats all you need to do