Hello,

You can easily translate them via .PO/.MO files. Watch this tutorial for more detailed information.
The button is a VC element so you need to edit it’s style via custom css. Add these lines into your custom css box:

.vc_btn3.vc_btn3-color-juicy-pink, .vc_btn3.vc_btn3-color-juicy-pink.vc_btn3-style-flat {
    color: #fff;
    background-color: #F4524D;
}

Add/remove attributes and edit the values to your wish.

Best regards!