Here's a simple DIY for creating your own two toned t-shirt, vertical style!
(I actually got the two toned idea from the Michael's website during Halloween season, which explains the colors I chose, just sayin'.)

Start off by choosing two shirts. I bought my shirts from Michael's craft store. When choosing your shirts, make sure they're similar in every way possible - length, neck line, etc.
If you're up for a challenge, you can use two different styled shirts and style them any way you'd like for your finished product. The possibilities are endless!

Fold the shirts in half, as evenly as possible, and just cut down the middle.
If you want to get a perfect cut - after folding the shirts in half, pin it together closer towards the fold. It'll help make it more secure.

After cutting, take one side from shirt one, and take the opposite side from shirt two. Pin together the front side, and then the back side. If you're not sure if you chose the right parts from each shirt, look at the neck line. They should match up.

When everything is perfectly pinned together, sew it up! I personally prefer sewing by hand - I love the full control. But if that's not your thing, go ahead and use that sewing machine.

Two extra steps I took to change up the shirt:
• I created a v-neck (looks kinda like a low-u-neck though) which is super easy. Before sewing the front of the shirt, pin the top by the neck line to the sides and then sew it up to create more of a v-neck.
• I took off both sleeves and swapped them. The green side has black sleeves, and the black side now has green sleeves.
These are both optional of course!

When it's finished, wear it proud!
I funked up my shirt with my well-matched neon green sunglasses pin.
Perfecto.