So a gluon in string theory may be an open string whose ends live on one or two branes? These strings have an orientation along the string? Does the orientation change direction if we reverse time, some where I thought I read that one can think of a flow along the string so if you reverse time the flow must reverse? Can we think of each end of the string as being associated with a color charge and an anti color charge, like red/antiblue? Thanks for any help!