Rstudio - Boxplot

Question

I have a graphic with a set of 3 Boxplot that all appear, depending on the code I made, in "gray" and I can’t change that color. I leave here the code I have in the script. I would ask for help to resolve this issue. Thank you.

C=list(performances_performanc_NN$Performance.rel,performances_performanc_SVM$Performance.rel,performances_performanc_RF$Performance.rel) Names(C)=c("NN","SVM","RF") boxplot(C,col = rgb(0.5,0.5,0.5,0.5))

Vidal