Leaking Toilet

My toilet keeps kicking on about every 15 or 20 min. I cant see water running in the toilet from the reservoir, so I put a llittle food coloring in the tank and sure enough the color went into the bowl. Sunday I put a quarter turn supply valve on and also took the float valve out to twist and turn the height of the water level as it was a little low to start with. I did not have problems with it before I did that so I am wondering if it is the flush valve or the flapper? Also if I remember right there is a new flush valve out that will not continue to fill up the reservoir.It seems to me I saw it ina a magazine or on the internet.Anyway thanks for your opinions. Got to get off of here now and head to work.

I am going to guess the flapper.

I'd bet money on the problem being the flapper. Since you get the dye into the bowl, that's the only way it can get there.