You can edit the color of your button within the CSS of the template. You should find this element selector within the template that contains the hex decimal to change out your color:
As for changing the text color of the button, you can do that in your Design Studio. Open up the form you would want to edit. Then on the upper right hand side in the Form Propery Panel you change the Font Color value as shown here:
You can set the URL of the PDF as your follow-up page for the form in the Landing Page Editor. Just select the form inside of it, choose Edit from the gear menu, and enter the adress of the PDF as the followup.
The best way would be to drag your form onto a blank landing page and approve it. Open your approved landing page, then using Firebug, right click on the form and select Inspect Element. This will show you the CSS being used for the form. You can overwrite the CSS by dragging in a Custom HTML box and add your own CSS to style it.