First of all, when we do our warmups, we often times have you grab bars to drill the lifts. This is the time to get used to the bar you are going to use for the lift as well as a time to get the blood flowing and really warm your body up.
Using the orange 15kg bars is fine if that is usually the scale you need to use, especially for the more advanced movements like the Overhead Squat and the Olympic Lifts. However, if you are working squats and deadlifts, or a lift that you are working over 75kg with during your strength, you should be grabbing those black 45kg bars for the warmup.
I understand we all fall into a routine, and sometimes warmup is thought of as kind of a throwaway, but we take the warmup period very seriously. We look at it as a time for the members to get a decent workout in before they even get to the platforms or the actual WOD, and a time to really drill the lifts and get the muscle memory down. If you are using a bar that is way too light for you, you won’t get all of that out of it and can even establish some bad habits if your repetitions of the lifts in warmups are no good. Challenge yourself with your bar choice in warmups and get something out of it.
Also, keep in mind that when we are doing the Olly lifts the bar is very important. The black and green bars spin at the ends because they are specifically made for Olympic lifting. The orange tape bars don’t. This is why we call them “training bars” because they are light enough for a newbie or someone that needs work on the movement to use them, but people beyond the “training” stage shouldn’t be using them. This is especially true if you are a regular in the All Levels classes.