Is it possible that the RND-type efflux pump, which is most common on gram-negatives, contribute also to the repulsion of non-drug chemicals (like dyes) trying to enter the cell?
Yes. For example, the AcrAB-TolC efflux system of E. coli and S. enterica can export various dyes, such as acriflavine, ethidium bromide, crystal violet, methylene blue and rhodamine 6G.
Article Virulence and drug resistance roles of multidrug efflux syst...