Why are a few invoices highlighted in purple and the others are all blue?

Thanks for raising your question regarding invoices highlighted in purple and blue, accounting418. 

Before we proceed, I want to make sure we're on the same page so that I can accurately address your concern. I've included a screenshot below to confirm if you are referring to the same area. 

The section pointed by an arrow shows a color guide with blue representing estimates and purple representing Unbilled income. However, if you meant something else, please let us know by adding a comment below. Additionally, it would be helpful if you could send us a screenshot to help us understand your situation better.

Your cooperation is highly appreciated, accounting418. I'll wait for your response. Have a nice day!