Get the legend right when using a bar chart with several bar colors

Hi all!
I want to creat a bar chart to show sales revenues for each month in 2018. However, in each month we sold only one of three possible products, so I would like to color the bar graph of each month in one of three colors, based on what was sold that month.
This is somthing I know how to do.
But when I try to get the legend to show the three colors with the name of the corresponding product, I can't. At least, not without ruining the chart itself. Can anyone here show me a way to accomplish this?
Thank you!

EDIT: here is the problem -
Doc1.pdf


you can see how to legend is presenting itself. what I would like for it is to have only 3 entries: pruduct A (blue square), pruduct B (orange square), pruduct C (grey square)

I think you'll need to clarify your issue - preferably by supplying a sample workbook. A legend always reflects what is in the chart.

That's not a workbook...

I'm aware of that. You need to rearrange your data so that you have three series plotted.