Hi Febin Gafoor,
It is only Alta Look and Feel for Release 12.2.5 and higher.
Your query is addressed in Look and Feel section of following Note
Oracle Application Framework Profile Options, Release 12.2.6 (Doc ID 2172925.1)
Hope this answers to your issue
Thanks for the response
I am referring to the below Themes that is already there by default in Oracle R12.2.6. Only concern is the theme is getting reflected, however the login page doesn't take up this theme. Is there any way we can get this to reflect on the login page to take up this theme.