When choosing a color for an accent wall, it's essential to consider the overall aesthetic of the room. Generally, if you're using the same color as the rest of the walls, your accent wall should be at least two shades darker to create a contrasting effect and draw attention. However, the exact shade difference can vary depending on personal preferences and the specific design style you're aiming for. Remember, the key to a successful accent wall is to create a sense of balance and harmony within the space, so it's crucial to consider all elements of the room, including furniture, lighting, and other decor.