At the left side menu, there's an option to register colors in OZmap. These colors will be saved to be configured on the elements.
Each element type has a default color, so your elements can follow that parameter or a pre-registered color.
To add a new color, select the "New color" option at the bottom of the screen, like in the image above.
You'll need to enter a name and select the color.
These colors will be saved to be set in the elements, as is the case with this box:
These colors will be available when adding new elements and when editing them, individually or in batches.