Unity Hex colors the same, but colors display wildly different.

In this image the square at the top of the circle is the same as the background color in terms of color value, but it looks completely different. The half blue circle is the same as the underlying blue circle, yet wildly different. Is there a color picker or something that allows me to match colors in Unity?

 

You didn't say what objects/components you are using. At first glance, it looks like one of the elements is a UI Panel object. And this object is dimmed by default and you need to set maximum transparency.