Rise: Focus Visible: what theme/button colors are supported?

Hello, For accessibility reasons, I'd like to change the focus rectangle's color in Rise. Currently, when the video (embedded in a Rise course) is in focus (using the tab key), the black focus rectangle is nearly impossible to see. Is there a way to change the color and even the stroke size of this focus rectangle's outline in Rise? The course will be used by 100s of learners so I'd like to make this change in Rise (versus relying on different browsers' default focus indicators). Thank you in advance for any recommendations.