im wanting to put up black lights outside but whats the difference from black light blue to normal black light ?
and someone told me but im pretty sure it isnt true but do you have to use a special ballast ?

They're basically the same thing. Only difference is the black light blue has a different glass material from black light. It filters off most of the visible light except UV.

No special ballast needed. F20T12 black light is same electrically as the F20T12/BLB. If your fixture takes any F20T12s. They'll take either bulbs too. As easy as changing bulbs.

The F20T12 is an example.

Yep FGS is correct nothing special just a different colored glass tube (wood's glass), and they are slightly heavier and if you want the best deal on a F40/BLB (T-12) lamp made by GE head to Lowes they are $8.99 and everywhere else wants upwards of $20 or more, even home depot for a tube usually of questionable quality, especially this time of year because lots of people like them for Halloween decor so they are real cheap knock offs..

we unfortunately dont have lowes in Canada

we unfortunately dont have lowes in Canada

My bad, your getting one in early 2018, I didn't think to check as I have like four around me and I figured there would be at least one in Winnipeg, find some where carrying GE lights and get them to price match from Lowes.ca website, Rona does this if you have a Rona that carries them, I know Rona carries GE lights but I don't know about the BLB stuff there...