[Plugin: Twitter Widget Pro] How to style the Follow button

The widget works fine. I’m trying to style the elements of the Follow button, which is generated in an iFrame, like this:

<iframe src="https://platform.twitter.com/widgets/follow_button.html#_=1318003510255&align=&button=blue&id=twitter_tweet_button_0&lang=en&link_color=&screen_name=GDegustationMTL&show_count=&show_screen_name=&text_color=" allowtransparency="true" frameborder="0" scrolling="no" class="twitter-follow-button" style="width: 300px; height: 20px; " title=""></iframe>

[Please post code snippets between backticks or use the code button.]

I tried modifying the display() function in wp-twitter-widget.php by adding Twitter parameter to $linkAttrs but it doesn’t work. How could I change the button color using button=grey instead of the default button=blue (which I cannot get to change)?

Thanks!

https://www.ads-software.com/extend/plugins/twitter-widget-pro/