Turn off ambient lighting not working?

I looked at some questions regarding disabling ambient lighting. The most popular suggestion was to turn the ambient light color to black. (I am trying to make my scene completely dark besides any lights I place) However, when I do this (And set the background color to black) I get this:

My desired outcome is for the pink square not to be visible unless in the light, But it is visible no matter where it is. How would I go about solving this?

I assume that since the object apparently uses no diffuse texture/has no diffuse texture found but needs one, that it shows the default pink color which might behave different in regards to lighting. Try using a properly set up material.