Hey Jin
On your home page I tested out the code and could see the background as black and text as white.

Here’s the complete code tested on the front of your site:
.tribe-events-list-separator-month span {
background-color: #000 !important;
color: #fff !important;
}
.tribe-events-loop .tribe-events-event-meta {
background-color: #000 !important;
Background: #000 !important;
color: #fff !important;
border: 0 !important;
}
You can test out removing the !important tag as well as matching up the precise colors.
Thanks
Courtney ๐