A 'recommended' property for form fields. (as opposed to the hardlined 'required' property)

I've been thinking how i could encourage form submissions to include information that would be useful but not a strict requirement. Traditionally the fields are either entirely optional OR fully required. There is no way to moderate and say that certain fields are encouraged more than other entirely optional fields.

i wondered about (https://moodle.org/local/chatlogs/index.php?conversationid=12177#c415393) something like a 'reminder' that has an amber asterisk or amber div background to an input field? that turns amber when the fields in the next tab index sequence are highlighted or unfocussed perhaps.

The field shouldn't prevent nor affect submission of the form and should only serve as an aesthetic reminder. Unlike the 'required' property.