css change in style.css for Garland theme does not get reflected

I am using Garland theme.

I do not have admin access on my machine. It has XP OS. Here is the problem i am facing.

It seems Garland theme generates a copy of some image files and two css files style.css and style-rtl.css in file directory. Here is the complete path
D:\Apache\htdocs\mysite\sites\default\files\color\bb-2287c747\style.css

Somehow the permission is set so that only Administrator can delete this file. Any changes that i make to style.css files for Garland theme does not get reflected since the style.css in files directory does not get replaced automatically. And I am not able to replace it manually since i don't have admin access, while the style.css file in files directory can only be deleted by Administrator.

There can be two solutions-
1) There is a way for the system to replace this style.css files under files directory, which i am not aware of
2) There is a way to ensure that access to files in the above directory stays with me and not the Administrator of the system

Thank you for reading a long one.
Appreciate your response.