[EDIT] See fixed test case here http://jsbin.com/dapiqopiqa/edit?html,css,output
(this works in Firefox but not Chrome)

Right now it doesn't work in any browser. Is that a bug? Should we spec it that way? (just curious)

https://wptest.center/#/hku8b7

div {
	color: red;
	animation: x 3s infinite alternate;
}
@keyframes x {
	to {
		all: initial !important; /*color:black*/
		font-weight: bold;
		background: yellow;
	}
}