message: Added the model index theme provider as an option for the carbon color when selecting the element-symbol color theme
diff: @@ -19,6 +19,7 @@ import { OperatorNameColorThemeParams, OperatorNameColorTheme } from './operator
  import { EntityIdColorTheme, EntityIdColorThemeParams } from './entity-id';
  import { assertUnreachable } from '../../mol-util/type-helpers';
  import { EntitySourceColorTheme, EntitySourceColorThemeParams } from './entity-source';
  +import { ModelIndexColorTheme, ModelIndexColorThemeParams } from './model-index';
  // from Jmol http://jmol.sourceforge.net/jscolors/ (or 0xFFFFFF)
  export const ElementSymbolColors = ColorMap({
  @@ -35,6 +36,7 @@ export const ElementSymbolColorThemeParams = {
  'entity-id': PD.Group(EntityIdColorThemeParams),
  'entity-source': PD.Group(EntitySourceColorThemeParams),
  'operator-name': PD.Group(OperatorNameColorThemeParams),
  + 'model-index': PD.Group(ModelIndexColorThemeParams),
  'element-symbol': PD.EmptyGroup()
  }, { description: 'Use chain-id coloring for carbon atoms.' }),
  saturation: PD.Numeric(0, { min: -6, max: 6, step: 0.1 }),
  @@ -63,6 +65,7 @@ export function ElementSymbolColorTheme(ctx: ThemeDataContext, props: PD.Values<
  pcc.name === 'entity-id' ? EntityIdColorTheme(ctx, pcc.params).color :
  pcc.name === 'entity-source' ? EntitySourceColorTheme(ctx, pcc.params).color :
  pcc.name === 'operator-name' ? OperatorNameColorTheme(ctx, pcc.params).color :
  + pcc.name === 'model-index' ? ModelIndexColorTheme(ctx, pcc.params).color :
  pcc.name === 'element-symbol' ? undefined :
  assertUnreachable(pcc);
  