Change state of object located in a scene after user has completed another scene

Hi. 

I am creating an eLearning aimed to provide learners with an understanding of the 7 stages of a 7 stage model.

I have created a main slide in a scene (scene 2) where the learner can click on each stage to be directed to each of the corresponding scene which has between 2-5 slides. Once they have completed the stage/scene they return to the main slide again to then select the next stage of the model.

I would like to change the state of the stage image to denote that they have completed that scene/stage.

How can this be done?

Can I create a trigger that will change the state of the image when the scene has been completed? 

Thanks!