Having a shot edit well with the previous shot is more important than exactly matching the hero shot. Try to use a full-frame stillstore, not split screen. Grading from memory helps you learn to make shots edit well faster.
Few things are more jarring in a scene than when two shots back to back don’t feel like they match. You’re watching a conversation between two people, a third person joins the scene, and the third person looks like he doesn’t belong because his skin’s the wrong shade or the background’s too saturated or the wrong hue. Even if the shot matches on a “technical” color value level, it’s more important that it matches perceptually. Shots need to edit together well so as not to jar the audience.
A good way to practice matching “perceptually” is not using a split-screen stillstore for reference (where you can exactly match the two shots), but using a full frame stillstore. This will make you grade from memory, which means that you’re matching shots based on perception, and will help you make sure shots edit well together. It also has the added bonus (with practice of course) of helping you to grade faster, since you’ll have a better memory for how a shot should look instead of constantly referencing your still store.