To answer this question, let's go through each option and determine whether it is correct or incorrect:
Option A) 7 - This option is incorrect because it suggests that there are 7 pigs on Smith's farm that have the same color as another pig. However, this is not true as the correct answer indicates there are no pigs with the same color.
Option B) 3 - This option is incorrect because it suggests that there are 3 pigs on Smith's farm with the same color. However, this is not true as the correct answer indicates there are no pigs with the same color.
Option C) 4 - This option is incorrect because it suggests that there are 4 pigs on Smith's farm with the same color. However, this is not true as the correct answer indicates there are no pigs with the same color.
Option D) 0 - This option is correct because it states that there are no pigs on Smith's farm with the same color. This is the correct answer based on the information given in the question.
Therefore, the correct answer is D) 0.