Hi @Senthoor_Mani_M.
under the Meta data of your alarm status object create a domId with the value of your choice
Under Styles/stylesheet.css
enter the following code
#alarmTable .ia_table__headContainer{
background-color:black;
}
Just change the #alarmTable with the domId value you use (always with an # first).
Then save your project and the modification should be applied to all alarm status table with the same domId.
Be aware that the advanced style sheet is available on gateway 8.1.22 and after.
To activate it right click on the styles folder and Enable advance stylesheet.
Fyi it's the same for an alarm journal table.
Regards
Arnaud