from memory you will have the following depending on the model of prosport gauge.
red +12vdc
blk -24vdc
org dash illum
grn signal
with the engine running remove the sense line (small clear tubing you just installed) and check that the pressure now drops to 0psi, this will confirm your wiring and the functionality of the gauge, if the pressure stays at +30psi then you have either wired it wrong of the gauge is bad. If the pressure drops to 0 then when you reconnect the tubing it goes back to +30 you may have tied it into the wrong place.
If you still have issues or dont understand, post up your installation instructions so i can see exactly what you have, photos of your wiring terminations would also help.