The lighter colour highlight indicates the default line / account. White background for the line is the default line.
The default line / account will be used to make outbound calls unless another line is selected or entered specifically for the contact chosen.
On many phones, from the idle screen, you can change the default line / account by pressing left or right on the navigation pad. Or from the menu:
On the T48G, from the idle screen, you can change the default line / account by touching the upper left corner of the screen. A menu will pop up - select the desired line / account.
On the W56H, from the idle screen:
On the CP930W, line selection is not possible. For other models please inquire with Support.
Yealink SIP-T21P-E2, Yealink W52P / W52H, Yealink SIP-T48G, Yealink SIP-T29G, Yealink CP860 (EOL), Yealink CP920, Yealink CP960, Yealink W60P / W56H, Yealink CP930W, Yealink SIP-T43U, Yealink SIP-T46U, EXP43