I think blue
because it isn't a very natural color
green is very natural...like plants
orange is too..it's the color of muscles
violet can be too, depending on what you're looking at
but blue, especially bright blue, often indicates that you shouldn't eat something...like a poisonous frog...
even the blue that is our veins isn't really a bright blue
it has a more violet tint

I think it would be more interesting as bright blue :)

You pass gas too far.