How do I add custom CSS to style my H5P in my company's branding?

Hi,

I am rolling out H5P components to a cohort of 5000+ learners in January for my Online High School.

I love using the H5P components, but I would like to custom brand them to display the fonts and colours of my school's brand. 

Is there a way I can do this? Please provide as much documentation or information as possible if you have it. 

Thanks so much,

Jamie