Weird but it may be nothing ....

I live close to a main railroad track coming from Canada down through Iowa, Missouri, etc. Usually the engines that pull these trains are yellow with black trim. Then about eight days ago I started to see some new engines. It may be nothing but it is unusual that so many different engines are suddenly appearing. The first new one I saw was bright red with a series of black "X"s on the side. The second one was beautiful. Light blue with gold trim. Really pretty! The third is a dead ugly grey, no trim and no markings other than a number. These new engines do not have Union Pacific or Canadian Pacific on them like the old yellow and black engines. No link because my living room window does not have one, lol. Am wondering if it means anything or simply that new engines are replacing the old ones.