Change image alpha without Image

One of the things I wanted to do in my game was have the player's heatlh be represented by an image slowly getting more transparent as their health decreases. However, while going back and forth between Visual Studio and Unity, I've kept getting error messages about the compiler needing to be clear of errors, and after trial and error (since Intellisense isn't working with Unity extensions) I've found that Image is the main culprit. For some reason, Visual Studio just does not like Image. Here's what I'm Using for that file, as well. I looked for other answers on here, Stack Overflow, and other sites, but everybody is just going "Use Image image [...]".