How to create custom theme for Google Form?

[Stefan Radziuk via StackOverflow]

I wanted an embed Google Form in my website so i grabbed embed code and pasted it in my page.

<iframe src="https://docs.google.com/forms/d/1u1NO8u4vu6Q9XuUNigo4qy22hjvRmL-HFIRVsgiaL9c/viewform?embedded=true" width="760" height="500" frameborder="0" marginheight="0" marginwidth="0">Loading...</iframe>    

(that's what Google gave me)

Everything is working fine BUT it's an iframe so I can't edit it's appearance using CSS. Google Docs' deafult themes don't match my site so I want to this page's CSS. I tried downloading https://docs.google.com/forms/d/1u1NO8u4vu6Q9XuUNigo4qy22hjvRmL-HFIRVsgiaL9c/viewform as html but this way I didn't get the css file. Do I have to create it by myself or there's another solution to my problem?

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