Add color coding to final DID document

[kimdhamilton]

The playground shows the phases of DID resolution. It would be useful to display the final DID document color-coded, demonstrating where the content came from. Some possibilities:

• color code final DID document (from phase 1, etc)
• highlight public key and/or other interesting fields derived from transaction

Because it's a JSON document, I use preformatting to ensure the json displays well. Unfortunately, I can't combine this with html colors. This HTML/CSS foo is beyond my ability