Cross your legs if your visiting the centre of Sheffield in the near future, because for the next two weeks fountains in the city centre will run yellow as part of a Tour de France themed art event called Paint the City Yellow, part of the 100 day long Yorkshire Festival - which also starts tomorrow.

Why? Well Today it’s 100 days until the Tour de France starts in Yorkshire, so far the county has prepared itself with a combination of the traditional - hiking of prices on hotel rooms and campsites, and the imaginative: a mountain of wooly bunting; plans to pull a piano up Cragg Vale by bicycle, now as we enter the home straight Yorkshire is taking thing up a notch, or several and the yellow fountains are just the start of what promises to be a Tour inspired cultural (and commercial) frenzy culminating on the 6th of July with some actual bike racing.

The dye being used to turn the fountains yellow is called fluoroscein and is is used a a trace dye in medical procedures such as angiograms and, as you’ve probably guessed from the name, it’s fluorescent so for maximum effect bright lights will be shone on to the water at night.

Paint the City Yellow co-organiser, visual artist Terry Wragg told the Sheffield Star: “The event is potentially spectacular, and definitely non- toxic.

This dye is incredibly strong, and the science behind the fluorescent effects is fascinating.”

The keen eyed amongst you will have spotted the phrase “potentially spectacular” because as Terry points out,

“It has been impossible to carry out any dress rehearsal, for obvious reasons, so anything could happen. We are doing it for fun, and hope people find the effects enjoyable.”

So what’s it going to look like? Well, we’ve created this helpful artists’s impression of one of the fountains in Sheffield that won’t be running yellow just to give you an idea.

The effect could undoubtedly be spectacular, but having looked at the various shades of fluorescein available our advice to the organisers is to make sure they don’t run the dye too thin especially in the Peace Gardens or city centre public toilets may struggle to cope, as for pub chucking out time that doesn't bear thinking about.