Can I change the colors used in the poll confirmation window?

Yes, when creating the link to the poll, click the "Show" text link next to the Advanced heading.

There you will see options to change the colors of the borders, background and heading text of the poll confirmation window.

Click on the square with the "Select a Color" text to choose a different color for each element, and preview how the confirmation window will appear.

When all of the settings for the poll are completed, click the Create Link to Poll button to proceed.