Can I Make My Adsense Ad Transparent?

Unfortunately the answer is no. You can not edit your adsense ad so that it will have a transparent background. The reason for that is because of an agreement with the google adsense program which says that the advertisers' ads must be clearly seen and that can not always be accomplished with a transparent background. So that is why there is a solid background color for the adsense ads.

The best alternative would be for you to pick a color - the most prominent color is advised - and use its color code to put on your adsense ad(s).