Improve styling of Multi-Selection button in UDW, by adjusting colors for the different allowed states in order to make a more clear color difference among them:

• c-select-content-button with a background #e5e3e3;
• .c-select-content-button .ez-icon with a fill fill: #878787;
• .c-select-content-button--selected with a background: #00825c;
• .c-select-content-button--selected .ez-icon with a fill: #fff;