I've come across many customer environments where they use multiple versions of Java in Windows. This is generally due to multiple applications requiring different versions of Java to function. While there are a number of ways to pick which Java is used by the Applications Manager's Java client(client.jnlp file), below is a very simple way to create a custom link to launch a client using a version of Java of your choosing.
Visit the Applications Manager's Intro page and download the client.jnlp file to any location. In this example, I chose to download to my desktop (C:\Users\phm\Desktop\Client.jnlp)
Create a shortcut by right clicking the desktop and selecting New -> Shortcut.
The shortcut will contain 2 parameters: The path to the version of javaws.exe used to launch the client and the path to the client.jnlp. In this example, my values are "C:\Program Files\Java\jre1.8.0_74\bin\javaws.exe" "C:\Users\phm\Desktop\client.jnlp"
Select "Next" and give your new shortcut a custom name. I chose "Java8.74.AM8" to represent the Java version and AM version. Select Finished.
Launch the new shortcut and review the "About Applications Manager" screen to see the correct Java version(Workstation Java) used by the client.