Buttons changing states on click instead of doing it conditionally

Based on the description, it sounds like grey is the Visited state. Visited is a built-in state, and an object will automatically change to Visited when clicked, without a trigger. 

• Here's more info about built-in states: PRIMER: Take advantage of built-in states - Articulate Storyline Discussions - E-Learning Heroes 

If that's the case, then use a custom state to indicate when a section is done. 

If you're already using a custom state, other troubleshooting is just guessing without seeing the .story file. If you upload it, someone might be able to solve the issue.

Here are the best practices for uploading a .story file:

• Only include slides that are related to the problem.
• Be sure objects, layers, motion paths, and variables have meaningful names.
• If there is proprietary content, replace or delete it. For example, replace proprietary text with “ipsum lorem” text.