GUIStyle.onActive

Настройки рендеринга при включении элемента и нажатии на него.

using UnityEngine;

public class Example : MonoBehaviour
{
    // Sets the text color of button to yellow when an
    // element is turned on and pressed down.
    void OnGUI()
    {
        GUI.skin.button.onActive.textColor = Color.yellow;
    }
}