The purpose is to having a tone variation of colour when mouse is over an image. Example very easy you could fit at your needs.
1 - Set up width, height and background #66CC00.
Take a Frame Rate equal to 30
2 - In Menu Insert, click Image. In 'Shape', select Clipped Image.
Click the icon image : a dialog box 'd open.
Select the image you want.
3 - In Timeline, You gonna set up the following effects :
Frame 0 Click 'AddEffect', then 'Place'.
Click Alpha. Set Alpha value to 10% for instance.
Frame 2 Click 'AddEffect', then 'Place'.
Click Alpha. Set Alpha value to 100%.
Frame 1 & Frame 3 in row Scene : Click 'AddEffect', then 'Stop'.
4 - In right zone, click tab Actions and hit Add Action et Add Event as mentioned in the image hereafter :
Add Action, then On Roll over. Then Add Event, then Goto Frame 2 of Scene1.
Add Action, then On Roll Out. Then Add Event, then Goto Frame 0 of Scene1.
I guess you have understood, at start, the image is pretty faint if mouse is outside its limits,
and image becomes quite normal as soon as the mouse is over it.
It's up to you to fit that example to your own project.