Within your Jomablue Instance, Category Names are able to be changed, however we strongly advise against this, as Categories are used across your entire Instance, and are not specific to the Event you are currently in. Changing a Category in one Event will change that Category in all Events.
To change a Category Name in Jomablue, click on Categories and then click on the Category you wish to edit. You will see a field for Category Name - set this to the desired Name and then click Save at the top-right of the page.
Immediately you will also see a warning in red - notifying the user that the Category Name they are editing will be used for all Events in your Instance (see below).
Once you have clicked through this phase, you will be provided with yet another prompt so that you are aware that this is going to affect all your events that are linked to this Category.