CA PC 3.6 on rhel 6.9
need to change CA Performance Center title in login console as attached screen shot which is highlighted .
I am unsure if that specific entry can be altered but if it can you would do so like mentioned here:
Customize a Theme - CA Performance Management - 3.6 - CA Technologies Documentation
At a high level, you copy a current theme, make modifications to it, load the theme and set it for your tenant (default tenant if no multi tenancy).