Why is access highlighted yellow for a person? This is due to the Use It Or Lose It (UoL) features recommendations. It's informing you that the person whose access is yellow has not used their credentials at any portals or readers contained in that access level in XX days. What you choose to do with this information is up to you. In the future, you can automate actions, like remove the credential, remove the AL, ALG, suspend the person, put an end-date on the credential.
In Portals, Access Levels, Access Level Groups, and Person> Access, you will see "Access Point Use Analysis Mode" or "Access Point Use Immunity Level, days" These settings are used to calculate the recommendation. I am in the process of writing up a knowledge article on this, but it will probably be a week or so before I get it created and published. I want to run some use cases and see how the settings in the four places affect each other.
For Access Level:
For Access Level Group:
If you look at people
1. Set the search parameter "Search" to "AO Recommendations"
2. Select a person
3. Select "Access Removal", bad name, it will be changed shortly.
4. You will see the recommendation.