If the apical meristem of a growing young plant is damaged, it will primarily affect the length of the plant. The apical meristem is the primary growth point located at the tip of the plant`s shoot or root. It is responsible for producing new cells that contribute to the elongation of the plant.

When the apical meristem is damaged, the plant`s ability to grow in length will be compromised. This can result in stunted growth or a complete halt in growth depending on the severity of the damage. The damaged apical meristem will no longer be able to produce new cells, leading to a reduction in the overall length of the plant.

The other options provided in the question are not directly related to the function of the apical meristem. The color of the flower, leaves, or taste of the fruits are determined by other factors such as pigments, environmental conditions, or genetic makeup of the plant. Therefore, damaging the apical meristem will not directly impact these characteristics.

In summary, if the apical meristem of a growing young plant is damaged, it will primarily affect the length of the plant.