He's not a pro-CCP Youtuber, but a pro-KMT one, the KMT being the CCP's opponents in the Chinese civil war. Their party flag is blue with a white sun (found in the upper-left corner of the Taiwanese flag), hence "deep blue".
I think this only exemplifies that the title can be hard to decipher if you're not deeply familiar with the context. If I understood this exchange correctly, the commenter above received the exact opposite of what the title was supposed to convey. The fact that I'm not sure either furthers the point.
The KMT party has shifted over the years to being far more pro-CCP than the other parties. Saying being deep blue and being pro-CCP is not disingenuous at all.