Initialize high contrast mode after the Controller is fully set up. Call this from the Controller after construction to apply high contrast if enabled.
Suspend high contrast mode visually (restore original colors). Called on blur to return the chart to its original appearance. The setting remains ON - this just hides the visual effect while unfocused.
Toggle high contrast mode on/off. Called from keyboard shortcut (C key).
HighContrastService manages the high contrast accessibility mode.
Key behaviors: