Hello everyone

I have installed Kubuntu 15.04 with KDE Plasma 5 on my notebook.

The problem is that I am not able to change the colour scheme.
Actually, to reduce eye-strain, I would like to use a dark theme, but I do not like
the pre-installed ones.
So:
If I choose a pre-installed theme from Settings-Colours-Scheme and then click "Apply",
the new colour scheme is correctly applied to the system (and to the applications such as
Dolphin, Kmail and so on).
If I either download a new theme or modify some colour of a pre-installed theme, and then click "Apply",
the colour scheme remains unchanged.

Is there any way to solve this?
Thank you

I'm running Kubuntu 15.04 with Plasma 5.3.2 and when I download a colorscheme via "Get New Color Schemes" and configure it, it is properly applied to both 4.x and 5.x applications.
Also, when I modify a colorscheme and save it as a custom one it works as expected.