I could be wrong about this, but it is my understanding that standard radiographic imaging commonly referred to as x-rays use a contrast agent (dye) comprised of iodine or barium. Radioactive contrast agents are reserved for CT scans. As Jerry suggested, if the dye didn't show up in parts of the image, it could indicate a blockage.
I have no idea what is meant by the "dye"... was your stress test with injections, nuclear injections?
My understanding is heart stress tests (always done by a cardiologist in my experience in New Jersey) check to see how well the heart muscles are getting oxygen. If heart arteries have partial or full blockage blood will not get oxygen to those muscles. So, it seems the "dye did not show up on parts..." may suggest a possible blockage.
In my experience when I "failed" a simple monitor stress test (I don't recall any injections) I was prescribed to take a nuclear stress test. Here I was injected with radioactive material that could be "seen" in my arteries. In my case this has (I've had at lest 3 nuclear stress tests over the years) shown possible problems that were found to be false when I underwent a heart catheter examination.
I wonder why you had a stress test, some symptom trigger it? In my case I asked for a stress test to get a better number on what my maximum exercise HR should be. This lead to lots of additional nuclear and other tests because I couldn't pass the stress test when I in fact didn't have the main problem it checks for.
Sorry if I wander... bottom line, see a cardiologist but if you don't have any serious symptoms I think you should think positive, nothing is wrong.