Private Gmail Contextual Gadget

I need you to develop some software for me. I would like this software to be developed using JQuery. I'm looking for someone to develop an in-house Gmail contextual gadget for our G Suite domain. This gadget would look at the potential recipients of an email (to, cc, bcc) to determine whether or not the addresses are interal or external to our domain. Depending on the recipient list the user would see different colors displayed in the "send to" text box element. For instance, if we're sending an internal email the user would see a blue background color in the "send to" box. If there are internal and external recipients then it would be yellow. If it is an email just to external domains the color would be orange.