CF7 Skins comes with many Styles which you can apply to any form with just a click (See Understanding Templates and Styles).
Create a new form or edit an existing Contact Form 7 form. Scroll down to the Skins section and click on the Style tab to view the list of available styles to choose from.
You can find a Style you like by using one of the following filters:
Clicking on the Details link below each style will give you more information about each style.
Click on the Expanded View link to see an even larger view of the style.
Or, use the Feature Filter to drill down into specifics.
Finally, there is a Search box at the far right of the screen.
When you find a style that meets your design requirements, you can simply apply it by clicking on the Select link. You will notice that the Select link will turn red and the text will change to Selected.
You can now click on the Save button to store the changes you made to the form and apply the style to your form.