Solfef is a great relationship that I wish we got to see more of. I would only add that I don’t believe arasol was ever confirmed to be in a specific quadrant, and works well as pale, while Solfef is definitely flushed. Also, while they occasionally seem similar, I think Aradia and Feferi have noticeable different attitudes. They’re not drawn to Sollux’s doom personality, but their relationship with death is different as a time player and a life player.