text color icon is not working--it becomes a highlight.

The box on the top right is labelled "highlight". It shows (highlights) the colours from the small boxes in the colour picker table in a larger format as you hover over them - presumably to make them easier to view/choose. The colour you actually choose (or enter in the text box) will replace the colour of the text you have selected.
The background and text colour tools both work the same way

Thank you,---but it is not working as described. The box on the left is text color, but when I click on "more colors" for text color the option that comes up creates a HIGHLIGHT color--it does NOT create a new text color. The same thing happens when I click on "highlight". In other words, "more colors" to change a text color is not working.

You can't click on "highlight"
You can click on text colour or background colour
When you choose more colours in either of them, they have a box labelled highlight. That "highlights" the colour you have picked if you pick a colour from the table of colours. If you click on the colour (in the table) it will be displayed in the "selected colour" box, and the hex code will show in the manual entry box below that
If you type in the hex code of the colour you want (e.g. #004166 for our TI "loyal blue)", that will show in the selected colour box, and that is the colour your selected text will change to on your web page.
Click your mouse to deselect the text and see the result.