You might be able to try RIT dyeing the tubing. Not sure if it requires a temperature excessively hot, though. Worth experimenting with a short length of it!
FortyTwoBlades
You could 3d print a hose using flexible TPU filaments and glue each section together and have it in the colors you want
SolarEclipse
My first thought with the tubes would be a fabric or leather paint, since those are meant to stick to flexible material. Otherwise, you may have to dye it or get tubing in yellow.
DrX
flexseal or plasty dip both come in yellow and have a spray paint can version also it will help paint stick
kotagezelman
Use paint for r/c car bodies (lexan) it is flexible.
TRFH
You could put a sort of yellow sleeve over the tube, I think captain Xavier did something similar with his proton pack
mateomangoplaysstw
The last time I painted that hose, I was painting it silver to accent the hoper unit. I stretched the hose just slightly, say 25 or 30% securing it with tape, then I lightly scuff sanded it with Red ScotchBrite, washed it, dried it thoroughly then I 'dust-painted'(sprayed very lightly)again at the slightly stretched 30%. The areas that needed touching up around couple of sharp turns were easy enough to dust a little more over those areas. It came out great. I don't know how it's aged, cause it was for a birthday present.
ScottBionicBlasters
Going to have to find them in yellow. Paint isn't going to work here at all. I'd suggest maybe looking at vacuumed cleaner suppliers for something like that perhaps....
malcifer
Is it crazy to suggest large diameter heat shrink tubing?
wess
Is this gonna shoot water or rival balls (tbh im kinda confused)