How to set up easy inclusion of an HTML snippet?

I’m trying to set up Zola to enable me to repeatedly include little bits of HTML (e.g. <span class="blue-tag">blue</span>). I thought maybe I could define these as variables and then use {{ blue_tag | safe }} in my Markdown, but this directive isn’t evaluated.

Is the reason for this just that directives like this are only usable in templates? Is there any way to do this sort of simple macro expansion from Zola Markdown sources?

Which version of Zola are you using? In 0.23 the whole content is a template so you can just use components for that.