> Looking at all of the state flags, it seems that the Virginia style "detailed seal on a blue field" is pretty common.

Wow, you're not wrong about that. I figured "seal on a background" would be a common type, but... why are they all blue?

Seal on white:

    IL
    MA
    RI

Seal on green:

    DE (?)
    WA

Seal on yellow:

    NJ

Seal on blue:

    CT
    ID
    IN
    KS
    KY
    LA
    ME
    MI
    MN
    MT
    NE
    NV
    NH
    NY
    ND
    OK
    OR
    PA
    SD
    UT
    VT
    VA
    WI