Produce 4 Lines
Using the Rectangle tool creates 4 vertical lines. Here, I used the Direct Selection Tool (white arrow) and held down the Shift key and Alt/Option key to duplicate the first line to create another 3 lines. I recommended to turn on the Smart Guides (View > Smart Guides or hit Command/Ctrl + U). Giving Colour to the Lines Let me tell you what I did.
I surfed through my Kuler colours collection and saved the swatches of my choice on the desktop and then loaded them in the Illustrator. To perform this function, go to the Swatches palette’s menu and choose Open Swatch Library and Other Library. Browse and choose the palette you have saved and press the open button.
On your screen a folder with the swatches in the new palette will appear. Click the folder to open it. The swatches will now be added to the Swatches palette of your document. Using your swatches give each line a different colour. You can also add a linear gradient effect too. Well, I have decided to use my fifth swatch to give a background colour for my creation by using a separate layer (which I locked each time I needed to when I was editing my lines shape).
Make with Mesh Option
Choose all the lines. Navigate to Object > Envelope Distort and from the submenu select Make with Mesh. Click the Preview button to view the mesh before you use it. To make things simple from editing I chose 4 columns (1 for each line) and 2 rows (to have only 1 handle vertically in the centre).
Drag on the handles to tweak the mesh shape of the lines. Make use of the Shift key a lot while you are working on the central points where the lines come close to each other.
Add More Colour Effect
Duplicate the layer with the lines mesh on the top of the original mesh. Click on the layer target circle on the right in the Layers palette and change the layer mode to Overlay in the Transparency palette. Move the shape bit until you get the shape you desire. When it comes to choosing the best layer mode completely depends on the colours you have selected.
Experimenting with the Shape
You can have a look at the shape in the landscape version. You can also put some more effects using tools like Warp, Pucker or Bloat. How about using a big brush? Choose a 400 pixel one to avoid small bumpy effects
In the image I decided to use the portrait version instead of landscape which is effective for Wrap effects. I also added some text by creating a curved path using the Pen tool. Then I chose the Type on the Path tool and added the text.