When you add a text box, it is added as a Comment. Comments, alsways go ON TOP of the page content.You can see that is is a comment because it shows up in the comment list.
When you sue the Add Text function, that's actually added to the page CONTENT. Which alwsy sts below comments and other annotations. I'd reoccomend using the commenting tool: Add Text Box. This combines the box and the text. It will be a comment, and you'll have very little control of how the text sits inside the box, other then horizontal justification. But the text will sit on top.
You may want to considering doing them separately, both as comments. This is fiddly, but you'll be able to reposition the text over the rectangle as you wish. To change the color of everything, use the Properties panel (Cmd/Ctrl+E). It's an old tool, but it still works very well. It's contextual, and so it's options change depending on what you have selected. More on the Properties Panel here.
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