Step 1: Understanding the reaction.
When 2-nitropropane reacts with nitrous acid, a reaction occurs that typically results in the formation of a blue-colored product. This reaction is part of the diazotization process where the nitro group gets involved in the formation of a colored complex.
Step 2: Analyzing the options.
(A) Yellow: Incorrect. The product is not yellow.
(B) Red: Incorrect. The reaction does not yield a red solution.
(C) Blue: Correct. The solution turns blue as a result of the reaction.
(D) Green: Incorrect. The product is not green.
Step 3: Conclusion.
The correct answer is (C) Blue, as the solution obtained when 2-nitropropane reacts with nitrous acid is blue.