I need an example application for when activating a digital output in Arduino UNO that sends a command to Nextion to change the color of a simple button.
Sorry, you ask in the wrong manner
- but perhaps wait and see, maybe someone with do for you..
Iteadlib CompButton example.
Nextion FAQs 4.1.19
Those attributes in green color can be edited by instructions.
.sta is not green. .sta field can not be changed from Arduino code.
Please refer to the Nextion FAQs and Nextion Editor Guide.