Can I change the radio button color in the Multiple Choice block?

I want to change the black radio button that appears after I select an answer in the multiple-choice block. Can this be done?

I'm not talking about the correct-answer color and the incorrect-answer color. I'm talking about the selected radio button.

The reason I ask is that after deselecting "Use white background on cards," the black dot cannot be seen against the custom blue background. 

Thank you.