User blog comment:B214/High School DxD BorN episode 1 review/@comment-25137187-20150407225649/@comment-16281343-20150408132056

Don't think so. Searched Volume 5 with the keyword "blonde". No result returned.

The description for Diodora is "A boy with a gentle atmosphere who had gracefully been drinking tea all through the uproar earlier also spoke."

Searched Volume 6 with the same keyword. Three results found: Asia, Kuisha, and Diodora's Queen.

Diodora was assumed blonde because he has the same color scheme as Asia's hair on the illustration.