String display formats can have two sections. The first is required and contains the format for strings; the second is optional and specifies how to represent NULLs:
string-format;null-format
In a string format mask, each at-sign (@) represents a character in the string and all other characters represent themselves.
This format mask:
[red](@@@) @@@-@@@@
displays the string 800YESCELT
in
red as:
(800) YES-CELT