In many cases, the police are going to tell you why you're being arrested. They could show up with a warrant, or the arrest may be pretty obvious -- such as when you're picked up for drunk driving after blowing a .10 on a breath test.
However, it's important for you to know that the officers don't always have to tell you what's going on. They do have the right to arrest you as needed and then tell you about the allegations and charges at a later date.
Most of the regulations about arrests say that officers should tell you what's happening if doing so is deemed to be practical. If there are other pressing matters, though, they can skip this step and it's still a legal arrest.
You may know that probable cause is required to make an arrest. The police cannot simply come to your home, arrest you for no reason, and then check things out later to see if the arrest was legitimate. They have to have a reason, and they have to show probable cause to get a warrant. However, they also don't have any obligation to tell you of this probable cause while arresting you.
Many people will complain while being arrested, even threatening to sue if they aren't told their charges before the handcuffs go on. That's because the myth that officers have to inform people immediately has really grown, despite being just that: a myth.
After an arrest, make sure you know exactly what legal obligations the police have so that you can know if your rights were really violated or not in Colorado Springs.
Source: FIndLaw, "Do Police Have to Inform You of Your Charges?," Brett Snider, accessed July 10, 2015