Understanding iOS Color Palette

I understand that we should be using color assets and UI Element colours.

However what I don't understand is how to use these to provide a color palette throughout the app.

If I use UI Element colours, will I not have a set of standard colours which will not match my custom pallet.

For example if I have a custom orange color that I want to use for labels, is there anyway of setting this to be used by UI Element colors

Is there a way to override or set the UIElement colours, or do they use my custom colours. I just don't understand how it is supposed to work
Understanding iOS Color Palette
 
 
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