It's Saturday 15th July 2017 and currently 00:44. I saw this strange object at around 00:35. I was looking out my window and spotted a bright orange light moving at a steady speed across the sky, it was definitely not a star, at first I thought it was maybe a plane and one of its engines was on fire but it was moving too fast to be a plane and it didn't appear to lose any speed or height as you might expect in that situation. Then I though it could be a landing plane since I live near an airport, again the same conclusion. I watched this bright orange light fly across the sky and occasionally dim as it went behind a cloud although it was still visible. It came out the first cloud and wntered the second, however when it came out of the second cloud it had changed into several dim red lights in a flat line, with the accasional bright flash of green to replace the red lights. It continued to fly over the airport and eventually got too far away to see anymore. I read up and though I could have seen a satellite but I've seen iridium flares before and they've been very different to this, this incident has left me confused and I'd love some insight as to what this might have been. Thanks :)
Your description matches that of a fireball, which are typically large meteors. As they enter the atmosphere they heat up and glow. The colour will depend on their speed and composition. As they get hotter, they often break up into several pieces, which follow the same trajectory. Much the same effect arise when old satellites or space debris re-enters the atmosphere.