Theme for Specific Application WPS

Please help on this problem.

I used this command in my wps-office-et.desktop under EXEC

env GTK_THEME=/home/rk/.themes/vimix-light-laptop-ruby /usr/bin/et %f

Also, I tried this one

env GTK_THEME=vimix-light-laptop-ruby /usr/bin/et %f

Specifically, I use WPS office and I need to assign a specific theme for this WPS office.

I am using Ubuntu 18.04 and WPS Office

Realizing that when I run it as root instead of normal user, it will work. But for normal user it won't work.

Left WPS Spreadsheet with Black Cells are in normal user, the right WPS Spreadsheet with White Cells are in root