Some favour the old classics; others favour the more ostentatious modern hybrids.
I offer this as a contender:
Lemon Yellow trumpets, and lemon yellow petals. 100% yellow. No frilly bits! All three of these compact blooms are borne on one slender stem about 18" tall.
The trouble is, I don't know it's name! I don't even remember buying it. I think perhaps it is one that came in a mixed bag I bought a couple of years ago. Does anyone recognise it? Even if you don't, do you like it or not?