Form warnings: Ability to change the icon and background of the form warning screen

I have an icon I would like to display instead of the one shown below

Can you walk me through how to do this. I know where to do it - I just need the code. I would also like to change the dark gray to white.

Thank you!

I have tried injecting some CSS code to the form to disable the icon and change the background color. However, it seems to be applied to the form itself. Since the error message is displaying on a separate page after submitting the form and redirecting to a different subdomain, unfortunately, it is not possible to change the icon/change the background color at the moment. 

Let me forward this thread to our backend team to see if this can be implemented in our later versions. I cannot promise that the feature request will be accepted. However, if accepted and once the feature is made available you'll be notified through this thread.

Thank you!