Unless you have perfect eyesight, the small screen of the Apple Watch may not be so easy to read, and while this is not the only thing you can do to improve readability on the watch, reducing the transparency can prove beneficial.
This feature exists because, by default, the Apple Watch interface uses transparency for the background in Glances, Siri, alerts and other features to make it look more attractive. With ‘Reduce Transparency’ enabled you may get some other benefits like a small increase in battery life and performance (any visual effect will use more or less battery and processing power), just don’t expect to see drastic changes in this department.
To enable ‘Reduce Transparency’ for the Apple Watch, you’ll need to launch the Watch app on your paired iPhone and navigate to ‘My Watch‘.
There, select General -> ‘Accessibility‘. In the ‘Accessibility‘ pane, tap on ‘Reduce Transparency‘ and toggle on the feature.
As soon as you enable ‘Reduce Transparency’ in the Watch app, you’ll be able to see the change on your wrist. The difference is subtle (you can see it in the image above), although disabling transparency does improve the contrast of the text a bit and makes it easier to read.
Be aware that for some Glances you might not notice the effect and as far as performance improvements go, only a few users have noticed a minor increase in speed when accessing various Glances. Nevertheless, you can limit animations on the Apple Watch to get a more significant performance boost, if that’s what you’re interested in.