It only stays red when I turn on the PC and when the Windows is starting appears, then goes blue. So I think like you said, that's how it got manufactured.
Okay, now one more test and this is vital. Google "BurnInTest" and download the software from passmark.com website. After installing the software, run "Maximum CPU Temp" from Quick Tests menu found at the menu bar.
The test should run for 15 minutes and it will automatically stop, displaying "Passed". If it throws error while testing, stop the process and must afford a new fan.
Most welcome, OP. You really don't need to worry about your computer's temperature if BURNINTEST shows 'Passed'. BurnIntest software is really powerful and efficient in reading the temperature under heavy load for each component in the cabinet. And that's why, it's a paid version.