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how to change the color and font of label of work item customization?
Accepted answer

Hi, Shubham
There is no features to change the work item item label's font and color currently.
There are some relevant RFEs and you may want to comment on it or raise your own enhancement request:
https://jazz.net/jazz/web/projects/Rational%20Team%20Concert#action=com.ibm.team.workitem.viewWorkItem&id=207403
https://jazz.net/jazz/web/projects/Rational%20Team%20Concert#action=com.ibm.team.workitem.viewWorkItem&id=258763
Comments

can it be done by searching java script files and making changes in it??

I am not sure if your above question refers to https://jazz.net/wiki/bin/view/Main/WebUITheming. It does not seem to me that it would apply to custom workitem.