The legends come out wrong in hist plots after adding the dev option

pls see:

bin/bob pad eval -e /idiap/user/amohammadi/swan/swan_{frame-diff-svm,lbp-svm-160,lbp-svm-64,qm-svm-160,qm-svm-64}/PA_F/scores/scores-{dev,eval} --legends frame-diff-svm,lbp-svm-160,lbp-svm-64,qm-svm-160,qm-svm-64 -l swan-face-pad.rst

which generates: eval_plots.pdf

Maybe we should multiply legends by 2?