Siemens SIMATIC PCS 7 Configuration Manual page 248

Configuring OS functions
10.3 Message system
picture, in which the message can be uniquely assigned. If messages occur in two process
pictures at the same time and these pictures are "ORed", the function branches to the first
process picture in which the the group displays come together.
The group display can contain the following information:
A Flashing interrupt signal
W Flashing warning
T Tolerance
S Flashing error message
O Operator request
X Message lock active in the area
This function is activated for an OS in the "Group display hierarchy" field of the "Message
display" tab in the OS project editor.
248
(white on red)
(black on yellow)
(white on blue, not flashing)
(yellow on black)
(white on blue, not flashing)
(white on gray)
Compendium Part A - Configuration Guidelines (V8.2)
Configuration Manual, 08/2016, A5E38166869-AA