created on 27th May, 2017
I found that when set <progress> color, no matter color or background-color, the color isn’t working. And the default color in chrome and firefox is different.
Then from this thread, I know that different browsers imprement this funciton differently.
progress::-moz-progress-bar { background: blue; } /*firefox*/
progress::-webkit-progress-value { background: blue; } /*chrome & safari*/
progress { color: blue; } /*IE10*/
if we need to combine id or class, just simply change progress to id or class.