Currently, the information provided does not specify how to change the category colors from pastels to bright shades in Outlook on a Mac. The Outlook object model allows users to define color categories, but the specific options for adjusting the brightness of these colors are not detailed in the available context.
You may want to check the Outlook settings or preferences on your Mac to see if there are options available for customizing the appearance of category colors. Alternatively, you can look for updates or support documentation from Microsoft that might address this issue specifically for Mac users.
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