How do I hide one chart and show other chart depending on case

I've a bar chart which show goal percentages, depending on percentages in values I've alerts to show different colors.which is working perfect so far.

Now the new req is, I've the Subtitle for the bar chart which is calculated field (Goal). the results of this subtitle are "Goal: xx.xx%" or "Goal: N/A"

so when it shows goal:N/A the user wants the bars colors to be changed i mean different from goal xx.xx%

how do I relate the subtitle to my bars.