Legend displays X axis labels instead of Data Series label when one bar color is changed

Using Excel 2010. I create a bar chart using data in a worksheet. If I add a legend, the legend displays the "Series Name" from the "Legend Entries (Series). By default, all bars have the same fill color. If I change the fill color of one of the bars, the legend changes to display the X axis labels, the "Horizontal (Category) Axis Labels". If I do not display a legend I can change the colors of the bars with no additional side effects. Does anyone know how to turn this automatic change off? I want to display the Series Name, not the X axis labels (they are already clearly displayed on the bottom of the chart.
Thanks for any assistance with this.

I can do that but then I have lost the automation - if I change the data series label in the spreadsheet I then need to change the chart(s). After creating charts in Excel I then copy them to a PP presentation which is then linked to the chart in Excel. I do a lot of this work and need to have the links working in the chart/data/label selection process.