The pink color indicates that that audio event is no longer lined up with, or sync'd with the video clip it had been part of . You've probably ungrouped it from the video, then moved it left or right. As long as you don't need it to be lined up with it's original video event then you can ignore the pink color.

The spacing is a bit more obscure. I'll start by summarizing that you can ignore it because it's completely irrelevant to anything and doesn't matter at all. Now, if you wanna keep reading past that ... Vegas draws as many frames as it can to fill out the space from the beginning to the end of the event. If those frames don't fill the area completely then it spreads them out a bit so that they are spaced evenly. If the event is short on the screen then there is more chance for the extra space to be quite large. Try zooming in and out (up and down arrows) a bit and you can see how the spacing changes.