I have been looking for days in the thousands of UI colors defined in :

3DSceneColors.dark
NodeGraphCommonDark.inc
NodeGraphDark.inc
UIDark.hcs <---------------It is here definitely because when I override grey, I can affect it.

the problem is that there are thousands of Grey(x)
The color is is grey 0.239 or 61 or #3D but it does not exist???

I am trying to make a color theme I like.
It is way too difficult, there should be a UI to do this.
Also the ? button open a web browser to nowhere -> empty page.

It should be called PARAMETERS, but I find nothing that could mean that.
It took me 4 days to get this far and it is probably not yet fully completed.

But I only need the parameters background with that stupid tab (don't forget the selected tab)

I have used a yellow color defined as _DEBUG to try to find where is that thing.
Thousands of trial and error and I could not pipoint its location.

Please help, this is maddening.

I will answer my own post because it may be useful for someone else.
Found the colors.
For the Parameter windows they are called GROUP(s)
there can be 4 groups one after the other, because this winodw is actually a list of groups.

GroupBodyX is the background and the 2 other things control the current tab look.

When I selected the "Render" tab of the parameter window, there are 2 groups there.

You can see that I have replaced the colors with NW_PARAMETERS_X_...


If anyone is interested in my theme, because it is a good starting point to make your own theme.
I only have 20 colors defined at the TOP of the file.
You only need to change those colors and I have named them for what they control.

I won't publish it yet, because there a lot hidden colors that I may have to change in the future.
There are 1 500+ colors Houdini.
Surely you can eventually come up with something that you like.

I created my Houdini Theme by sampling colors in Gimp from a Blender Theme mixe with an old LightWave3D theme.

There should be a more detailed tutorial about how to make a theme in Houdini.
As soon as I find time, I will make such a video to explain the intricacies of the 3 files that needs to be modified + another hidden settings to change the viewport background "theme"

There are 3 files to create a theme in Houdini

UIDark.hcs controls most the ui the colors
NodeGraphDark.inc controls the network (where you place your node) colors
3DSceneColors.dark controls the 3D viewport colors

You need to copy those files from the installation folder
/oopt/hfs19.5/houdini/config
to your local user folder
~/houdini19.5/config

Then you have to select your theme in top menu : Edit/Color Settings...
And last, you have to select your viewport theme in
Display Options: world/Background/Color Scheme

I will make a video tutorial eventually, the other youtube videos were a great help, but they never touched inside those files.

Thank you for this - it's exactly what I needed to know : )

Do you happen to know what needs to be modified in order to change the values from bold to custom color (when modified)?