Adding HTML tags to a blueprint YAML file

Is there a simple way to add HTML tags to my YAML file? I am trying to edit the appearence of returned values from a structure field inside the panel. I want some items bolded and some items inset under it, but if I add a colon anywhere inside of the HTML it breaks.

I am using the flipping example from here https://getkirby.com/docs/cheatsheet/panel-fields/structure, where he formats the entry section.

Here is my code.

entry: >

 <strong>{{style}}</strong><br />

 <span style="margin-left&colon; 10px">length&colon; {{length}}</span><br />

Should work:

    entry: >
     <strong>{{style}}</strong><br />
     <span style="margin-left&#58;10px">length: {{length}}</span><br />