Step 1 :Julio has a choice of 3 pairs of slacks (2 tan and 1 gray), 3 shirts (white, gray, and yellow), and 2 red ties if he wears the blue jacket.
Step 2 :The total number of outfits he can wear with the blue jacket is calculated by multiplying the number of choices for each item of clothing.
Step 3 :So, the total number of outfits is \(3 \times 3 \times 2 = 18\)
Step 4 :Final Answer: The number of outfits Julio can select if he wears the blue jacket is \(\boxed{18}\)