Need help with TablePress / Failing to change BG and hoover color of first row

I am an absolute rookie with WordPress, and I am currently building a few tables with the TablePress plugin. Everything works well, but I have a small issue with the color of the first row. It is blue, but I would like it to be red, specifically #fc1b0a.

There is a space for CSS classes in TablePress, but I haven't managed to get it to work. Is there a way to change the color of the first row and the hover color as well?

https://preview.redd.it/bt8x2j6x38md1.png?width=1919&format=png&auto=webp&s=e94d5ee580de155e5802797177386b4b1983194c