Consider pairing a harrington jacket with a dark green crew-neck t-shirt for a day-to-day outfit that's full of charisma and character. If you want to easily dress down your outfit with footwear, why not complete this outfit with black athletic shoes? Keep this combination in your front hall wardrobe come warmer weather, and rest assured, you'll save time getting dressed on more than one morning. When it comes to casual outfit ideas for teenage guys, this getup is ideal.