availableColors not working

Need Help
#1

I’m trying to get aviableColors but I’m getting an error:
The model class RainLab\Translate\Models\MLThemeData must define a method \My\Plugin\Models\Styles::myColorList() returning html color HEX codes for the 'bg' form field.

In themes/default/theme.yaml I added colorpicker field:

bg:
    label: 'BG color'
    type: colorpicker
    availableColors: \My\Plugin\Models\Styles::myColorList
    allowCustom: true
    allowEmpty: true
    showAlpha: true
    span: auto

In styles model I added:

<?php namespace My\Plugin\Models;

use Event;

/**
 * Model
 */
class Styles extends Model
{
    public function myColorList($fieldName, $value, $formData)
    {
        return ['#000000', '#CCCCCC', '#FFFFFF'];
    }
}

How to make it work?

#2

Theme.yaml is not expecting form field.

The theme information file theme.yaml contains the theme description, the author name, URL of the author’s website and some other information.

#3

If you dont need the logic with color generations, just use the colors as array:

label: 'BG color'
    type: colorpicker
    allowCustom: true
    allowEmpty: true
    showAlpha: true
    span: auto
    availableColors: ['#000000', '#CCCCCC', '#FFFFFF']