Bec Helman

So I am wanting to be able to put colour like this effect throughout an image or text font........ In the styles box there is metal, neon, retro etc etc but no rainbow as I've seen on other peoples affinity designer.....

I have not long downloaded affinity designer, love it, but I need the rainbow effect that's shown on many tutorials but its not in my effects box.... Anyone know how and where I an get that effect and others?