Hi,
it simply doesn´t matter. If the vector is in one direction then probably the sign of the value is negative...
According this picture: (assuming the bottom line is GND and all voltages are referenced to GND)
V+ is positive
IC+ is positive
(multiply both and get "positve" power, which means the OPAMP consumes power)
V- is negative
IC- is negative
(multiply both and get "positve" power, which means the OPAMP consumes power)
Io is positive and negative
Ip, In will be close to zero and may be positive as well as negative.
It´s all a question of "point of view".
Klaus