Hi Kristen,
The short answer is that CODAP does not provide any way to adjust the numeric legend color scale. As far as I know you are the first person to express a desire for this. Four years ago when we implemented the feature we thought users might want to adjust things but decided to wait and see. Now I’ll certainly add your feature request to our list.
Perhaps you could say a bit about the context in which you are using CODAP and how it would help you to make these adjustments?
Thank you!