Whether by accident or intentional, Switch's firmware update to Version 9.0.1 has removed a small feature. As you can see in the image above, the Switch usually shows a quick burst of color that corresponds to your Joy-Con when you slot it into the system. For whatever reason, that feature is now missing. Obviously the Joy-Con still works, but you don't get the added bells and whistles of seeing the color splash. Not a big deal by any means, but something worth pointing out.
QUELLE und TEXT: https://gonintendo.com/stories/345877-switch-firmware-9-0-1-removes-joy-con-attachment-color-effect

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