Legend For Grouped Charts

[sweet12prof]

(I checked the discussions threads much later after making the post only to realise my concern was asked before, but since it was unaswered years ago im leaving this.)
Hello all,

I hope this finds everyone well. Would like to start off by thanking all the devs for their hard work. This library is priceless, started using it fairly recently and it has been a blessing. I have a little problem though, and i will be very happy for any help i can get.

I am currently using bar object to plot a grouped chart. I wanted to use the legend to uniquely identify the different bar colors but it appears it only picks the first string of the legend object's string vector as the name for the different colors. I have a simple example as follows

  std::vector<std::vector<double>> vals{{1,2},{3,4}, {5,6}, {7,8} }; 
  legend({"a", "b", "c", "d"}); 
  bar(vals);
  show();

Will appreciate any help i can get. Thanks in advance!