The colour of the fuel soft factor triangle of a HQ has NOTHING to do with its stocks. A HQ that is green fuel wise can have stored 0 or 1000 fuel dumps.You can also see the green eared panzer corps full of fuel is swapping out to re-fuel than tanks.
Swapping motorised units between HQ because of stocks is a tactic to some degree, but the cases where you can build significant stocks in HQs are rare, at least if everything is working as intended by morvael.