1fe9841a_on_Manager___LimeSurvey_Manual__Meaning
[Color] red text [Sample] Sample [Tooltip] warning message [Comments] If you use one of the assignment operator (=) that operator will be displayed in red text. This is meant to help prevent accidental re-assignment of values when you really meant to check whether a == b instead of setting the value of a = b. [Meaning] 
assignment operator
Expression Manager - LimeSurvey Manual
Meaning