def testAddScheme(self):
     """Test adding a scheme to a registry"""
     registry = QgsColorSchemeRegistry()
     self.assertEqual(len(registry.schemes()), 0)
     recentScheme = QgsRecentColorScheme()
     registry.addColorScheme(recentScheme)
     self.assertEqual(len(registry.schemes()), 1)

 def testRemoveScheme(self):
     """Test removing a scheme from a registry"""
     registry = QgsColorSchemeRegistry()
     self.assertEqual(len(registry.schemes()), 0)
     recentScheme = QgsRecentColorScheme()
     registry.addColorScheme(recentScheme)
     self.assertEqual(len(registry.schemes()), 1)
     # remove the scheme
     registry.removeColorScheme(recentScheme)
     self.assertEqual(len(registry.schemes()), 0)
     # try removing a scheme not in the registry
     self.assertFalse(registry.removeColorScheme(recentScheme))

 def testPopulateFromInstance(self):
     """Test adding schemes from global instance"""
     registry = QgsColorSchemeRegistry()
     self.assertEqual(len(registry.schemes()), 0)
     registry.populateFromInstance()
     self.assertEqual(len(registry.schemes()), len(QgsApplication.colorSchemeRegistry().schemes()))

 def testAddDefaultScheme(self):
     """Test adding default schemes to a registry"""
     registry = QgsColorSchemeRegistry()
     self.assertEqual(len(registry.schemes()), 0)
     registry.addDefaultSchemes()
     self.assertGreater(len(registry.schemes()), 0)

 def testCreateEmpty(self):
     """Test creating an empty color scheme registry"""
     registry = QgsColorSchemeRegistry()
     self.assertEqual(len(registry.schemes()), 0)

 def testAddDefaultScheme(self):
     """Test adding default schemes to a registry"""
     registry = QgsColorSchemeRegistry()
     self.assertTrue(len(registry.schemes()) == 0)
     registry.addDefaultSchemes()
     self.assertTrue(len(registry.schemes()) > 0)

 def testInstanceHasDefaultScheme(self):
     """Test global color scheme registry has default schemes"""
     registry = QgsColorSchemeRegistry.instance()
     self.assertTrue(len(registry.schemes()) > 0)

 def testCreateInstance(self):
     """Test creating global color scheme registry instance"""
     registry = QgsColorSchemeRegistry.instance()
     self.assertTrue(registry)

# coding: utf-8
from qgis.core import QgsColorSchemeRegistry, QgsCustomColorScheme
from qgis.gui import QgsColorSchemeList, QgsColorSchemeModel

color_scheme_registry = QgsColorSchemeRegistry.instance()
schemes = color_scheme_registry.schemes()
project_scheme = [s for s in schemes if isinstance(s, QgsCustomColorScheme)][0]

color_scheme_list = QgsColorSchemeList()
# Doing
color_scheme_model = QgsColorSchemeModel(project_scheme)
color_scheme_list.setModel(color_scheme_model)
# or below do the same: change color in the component
# First option is lower level when you need to reuse
# the model in another component
color_scheme_list.setScheme(project_scheme)

color_scheme_list.show()