"Subscribe" button colour

hello,

I added a widget MailPoet into the widget in footer, but I cannot see the button “Subscribe” clearly. Font colour and button colour are almost the same. I need to change it. Can you help me with this, please? Check the screenshot below, or visit my website http://www.mysmesk.sk

http://screenshot.co/#!/a89c7382e1

Thanks!

https://wordpress.org/plugins/wysija-newsletters/