Hobby shops dealing with fuel engine powered cars or planes have small diameter fuel line that is the correct size for these connector hoses. It is a silicon compound, and generally comes only in bright "neon" colours. After a long soak in gasoline it doesn't show any degradation, plus these hoses are really only vents anyway and don't carry fuel. Sonce they are between the carbs they are not visible with the carbs mounted so the colour not a problem IMO.