Just seems to be the colouring of the flux coating.
I've got 6013's that are grey, (Lincoln, I think) and some others that are red, which I think are "Bohler Thyssen"
CJ
thanks, i just got some red 6013's, also what are 7016's used for? thanks
Basic low-Hydrogen electrodes.
See here:-
http://www.mig-welding.co.uk/electrode-classification.htm
And here:-
http://www.mig-welding.co.uk/wiki/Electrode_Reference_Chart
CJ