I've been using the new Apple Watch Series 6 for a few hours. These are the 5 biggest changes I noticed right away.

Lisa Eadicicco/Business Insider

• Apple announced the Apple Watch Series 6 on Tuesday, introducing blood-oxygen monitoring among other improvements.
• The watch also comes in new blue and red color options.
• Overall, the Series 6 seems like a modest improvement over the Series 5, but broadens Apple's health ambitions.

Apple finally unveiled its anticipated Apple Watch Series 6 on Tuesday, a refreshed model that comes with a faster processor, a slightly brighter always-on display, and the ability to measure blood oxygen levels, among other features.

The Series 6 is Apple's new flagship model, which it launched alongside the Apple Watch SE — a less expensive model that lacks features like an always-on display, an ECG monitor, and the blood oxygen reader.

Overall, the Series 6 appears to be a modest upgrade from the Series 5 that builds on Apple's efforts in health and wellness. The new ability to measure oxygen saturation is the biggest health-oriented upgrade to come since Apple introduced the ability to take an ECG on your Apple Watch with the Series 4.

But Apple isn't the first to offer such a capability; devices from Fitbit, Garmin, and Withings do, too.

Here's a closer look at the Apple Watch Series 6 in the limited time I've used it so far.