Overruling the font colour on the starting page or when you use the brand colour

Hi, 

I was asked by my customer, who has a yellow brand colour (#fddc05) to change the font colour from white to black, to make the Title better readable. 

Can You help me with this request? I know how to change the "brand colour" in the setting, can I overrule the white fond colour somewhere?

Thank You in advance!