Unless your signature is a pure image (JPG, etc.), then the way it appears on the recipient's end is almost completely determined by the way the recipient has their email client set up, and you have virtually no control over this.
To ascend my soapbox for a second, email was never intended to contain colors, graphics, font stylings, or anything other than plain, boring text. All support for text stylings and images are "hacks" upon the original email standard (even email "attachments" are "hacks"), and, as such, cannot be controlled 100%.
If you send me a very stylized HTML email, but I have my email client preferences set up to only view as plain-text, then I won't see anything but a bunch of gibberish and HTML code on my end -- and there isn't a single thing you can do about it from the sender's side.
As Satcomer said, the best you can do is query the recipient about their email client's settings, and what types of stylings and formattings they have their email client set to view. Again, if you send me something formatted as 12 pt. Arial, but I have my email client set to view everything in 48 pt. Times New Roman, you can't do anything to force me to view your email in 12 pt. Arial.
I highly recommend focusing on the substance and content of the email, rather than how it looks. Abandon colors and text stylings, and reserve those things for web pages rather than email. Create your signature as an image, not as a collection of images and stylized text in HTML format, if you want what you send to look identical on the recipient's side as it does on the sender's side. Even then, though, if I force all my mail to be received as plain-text 9which many people do), even an image for the signature won't display properly.
Just be aware that you cannot force 100% of your recipients to see the exact, same email you send if you use anything other than plain-text.
