IntelliJ IDEA CE not highlighting keys in .properties files

(I'm using the Mac) In Intellij Community Edition I'm using the default color scheme for the properties files:

• with the .properties files, the colors are not being applied to the keys, whereas the values are correctly green
• with the .yaml files, the colors are all good

I already double checked that the folders are marked as Resources Root and Test Resources Root... how should I solve this issue?

A grey color of a property indicates that the property is unused. You can hover the property with a mouse cursor to check it. Probably, you don't have a Spring integration if you use Community Edition and that's why IntelliJ IDEA marks these properties as unused.

In other hand YAML files in IntelliJ IDEA don't have indication of unused properties and that's why all the keys in YAML file are highlighted as used.