我拥有全部.键是:after修饰符和is-focused类.只需将#FAFAFA替换为您的indigo-pink，它就可以正常工作了.这仅仅是概念的证明.检查小提琴.它的文字标签也有颜色.

I have it all. The keys are the :after modifier and the is-focused class. Just replace #FAFAFA with your indigo-pink and it should work for ya. This is just proof of concept. Check the fiddle. it has the text label colored too.

.mdl-textfield.is-focused .mdl-textfield__label {
    color: #FAFAFA;
}

.mdl-textfield__label:after{
    background-color: #FAFAFA;
}

https://jsfiddle.net/90u6Lxc4/30/