i don't think that color or bold signature will help you
agree, Signature keyword animation doesn't matter,only matter backlinks.Signature is reference of your websites.It provide direct backlink to your website.
Signature links are good for SEO, but the CSS of them doesn't matter at all. Styling does, however, increase the chance of people clicking your link by getting their attention.
I believe that having signatures in bold or in a different colour can help in a way that it will draw people's eyes to it and possibly click through on it. With this, you will be able to gain visitors to your site. However, when it comes to search engines, I don't think it has any bearing at all.
Signature helps us to get bank link and generate web traffics. We use it only for create back link on high ranking website for getting more and more web traffics.