One may use data defined override in order to set symbol colours. The expression editor says, the expected format would be
string [r,g,b,a] as int 0-255 or #AARRGGBB as hex or color as color's name
For lazy coding with few colours the last approach is the easiest (in my opinion). Still, I was wondering if there's an exhaustive list of the colours accepted as arguments? I looked through the official documentation and googled some, but probably didn't use the correct terms.
Can someone provide me with said list of colour names?