Using color in figures for economics journals
Read the author guidelines for the journal you intend to submit to.  Within any field there is variety.

But always assume the paper will be read in B&amp;W, and make it fall back gracefully.  This may be by the reviewer, or it may be by a reader who prefers to work on paper and has easier access to B&amp;W printing.  This also goes quite a long way towards making it accessible for colour-blind readers.  

"Helpful but redundant" is a good description of what the colours should be.  Note that if there is a print version with monochrome figures, the journal will probably require that it's useful n that format; I've never come across journals that will accept two versions of the same figure (but I'm in a different field)