Hi,
thanks for your suggestion. But it is not so simple (read the note below)
for now you can use a CSS code like this:
#jsn-form.flat li[data-link="ALIAS-FROM-NAME"] a{
background:red !important;
color:white !important;
}
replace "ALIAS-FROM-NAME" with correct value (you can read it from browser inspector).
NOTE: "ALIAS-FROM-NAME" is not the Alias of the fieldgroup, it will be generated from the Name of fieldgroup. It is so because Easy Profile extends Joomla user management - not replace - and Joomla edit profile/registration layout does not expose fieldgroup alias in the output