Keep Coding

I know there already is an answer to the question here:
How to add new(customized) Theme colors to Powerpoint using VBA
But it didn't work. And as I'm not allowed to comment there (not enough reputation) I'm sorry for opening up a new question. (Dear admins - this isn't really clever in my opinion. Now we have two threads on the same thing, just because I'm not allowed to comment.)
Back to topic:
http://echosvoice.com/wp-content/uploads/pptfiles/customcolors.pdf
I followed the instructions of Echo, recommended in the other thread, but it didn't work. I have ppt2010 and tried with a THMX, a POTX and a PPTX. It's always the same. I rename the file by adding a .zip - I extract the ZIP - I copy Echo's example code and paste it right before /a:theme in theme1.xml file - I save it - I zip the whole folder - I delete the ZIP Extension - and it's corrupt. When I doubleclick, PPT opens without a slide. When I got to "open" and choose the template, I get an error message. "Repair" doesn't help. - What am I doing wrong?
(Somewhere else I read, I have to add this to every theme-file, but it doesn't make a difference)

Be kind to yourself. Use 7-zip (free) to open the PPTX (it can open them directly w/o having to rename them, and won't corrupt the files).
Alternatively, rename the file to zip, doubleclick to open the zip in Windows Explorer, drag any file you need to edit to the desktop, edit it there, drag it back into the still-open zip, then close the zip.