Colleague with zero experience paid equally to me. My male colleague blurted out recently that he's looking forward to getting that $2,000 paycheck.

I stared in shock as that's what I get and I've been in this industry (horticulture) for 19 years now. My colleague has 0 experience in this field. I have a 4 year college degree in English, a minor in Botany. He has a 4 year teaching degree, yet hasn't taught a single class due to a felony DUI several years ago. I did confront my boss regarding this wage issue. He said simply, "Well, you and Chris do the same job and I'm not going to pay him $2-$3 less." My response was, "I'm not asking you to do that.", thinking he'd get the idea that I deserve a large raise. When I started at this particular company 6 years ago, I had already 12 years in the Hort industry and my current boss even sold perennials to and dealt with my employer for 10 years. He knew me, knew I was a great employee and I worked for a good company, so I was shocked when I was overlooked and they hired a guy who had no work experience in this industry, but he did have a 4 year degree in Horticulture. Fair enough, however, I was hired as well, but paid $11 per hour while this guy, fresh out of grad school, (yes he did get a Master's) made $18 per hour. We did the same job then, so why now am I getting the run around from my boss? Why was it ok THEN to pay me so much less than my colleague for doing the SAME job and now it's not ok to pay my colleague so much less AND he has 0, I repeat 0, experience? My boss will not answer the above questions. He simply changes the subject. I have certifications I won't bother to list, as they're industry related and boring to the outsider, my male colleague has none of these certifications, I'm always on time, never call in sick, always respectful, get along with my colleagues, always take up overtime when offered, so I'm really quite perplexed here as to why I am getting screwed. Male vs female is all I can come up with in this scenario.