[tryfos79]

@tryfos79 

For the icons errors, try looking in the addons/packages folder for multiple versions of these addons. I had a similar problem. I just deleted the oldest versions and the errors went away.

No, it's not that, I have deleted all related addons. Installed just studio colored.
I still get all these errors , especially in MyVideoNav.xml:
2019-09-25 14:29:51.868 T:5640   ERROR: CImageLoader:oWork - Direct texture file loading failed for resource://resource.images.studios.coloured/
2019-09-25 14:29:51.868 T:5620   DEBUG: [Warning] CGUITextureManager::GetTexturePath: could not find texture 'flags/videocodec/'
2019-09-25 14:29:51.869 T:5620   DEBUG: [Warning] CGUITextureManager::GetTexturePath: could not find texture 'flags/resolution/'
2019-09-25 14:29:51.869 T:5620   DEBUG: [Warning] CGUITextureManager::GetTexturePath: could not find texture 'flags/aspectratio/'
2019-09-25 14:29:51.869 T:5620   DEBUG: [Warning] CGUITextureManager::GetTexturePath: could not find texture 'flags/audiocodec/'
2019-09-25 14:29:51.869 T:5620   DEBUG: [Warning] CGUITextureManager::GetTexturePath: could not find texture 'flags/stars/3D/'
2019-09-25 14:29:51.869 T:5620   DEBUG: [Warning] CGUITextureManager::GetTexturePath: could not find texture '$VAR[styleratingstars,,0.png]'

But also in Pointer.xml
2019-09-25 14:48:24.885 T:6036   ERROR: CImageLoader:oWork - Direct texture file loading failed for resource://resource.images.studios.coloured/
2019-09-25 14:48:24.886 T:6036   ERROR: CImageLoader:oWork - Direct texture file loading failed for resource://resource.images.recordlabels.white/
2019-09-25 14:48:24.886 T:6036   DEBUG: CTextureCacheJob::GetImageHash - unable to stat url resource://resource.images.recordlabels.white/

In my IncludesVariables.xml I see the following entry:
</variable>
    <variable name="value_mediaicons_path">
        <value condition="String.IsEmpty(Skin.String(resource.images.mediaicons.path))">resources/</value>
        <value condition="!String.IsEmpty(Skin.String(resource.images.mediaicons.path)) + Skin.String(resource.images.mediaicons.path,resource://resource.images.mediaicons.white/)">resources/</value>
        <value condition="!String.IsEmpty(Skin.String(resource.images.mediaicons.path)) + Skin.String(resource.images.mediaicons.path,resource://resource.images.mediaicons.coloured/)">resource://resource.images.mediaicons.coloured/</value>
    </variable>

Is this correct? The colored studios addon is in /resource.images.studios.coloured

Can someone explain what this "Direct" means? The funny thing is that colored studio logos appear just fine, only with a little delay. So how do they actually work?        

Yes the 'colored studios addon' is in .../resource.images.studios.coloured

Understanding the problem
There are three different addons being referred to here:
1. resource://resource.images.studios.coloured which refers to Studio Icons - Coloured Addon (this affects studio logos e.g DC comics, Marve Studios etc). 
2. resource://resource.images.mediaicons.coloured which refers to Media Icons Pack for Aeon MQ 7 - Coloured Addon (this affects media flags e.g 4K, HDTV, AUDIOCODEC,)
3. resource://resource.images.recordlabels.white which refers to Recordlabel Icons - White Addon (this affects record labels/producing company in music e.g Tuff Gong)

Apart from the 3 above, other errors in the logs comes from the skin texture files (flags/videocodec/', 'flags/resolution/' etc).

The common ground here is that all the errors are related to images needed by the skin.

The skin is requesting for these images, and somehow KODI cannot find them. Either because the mentioned addons holding the images are not installed or because the images are supposed to be in the skin folder and they are not there.

From these errors, my assumption is, you are using Aeon MQ 8 Multimod by @latts9923. I could be wrong. 

By default (without Studio Icons - Coloured Addon) this skin can show Studio logos albeit non coloured. It is possible therefore for your Studio logos to work correctly even when the addon is throwing errors but I do not expect the logos to be coloured. The possible explanation to the delay is that the skin tries to load the studio images from the addon first, which fails then it reverts back to default. I can't say this is the case for sure, just an assumption.

Possible solution
The solution is to provide the images the skin needs.
1. Make sure you followed the installation procedure for the Aeon MQ 8 Multimod properly. The mod should contain within its folder the extra texture files it needs. This should rectify the errors related to "texture 'flags/"
2. You said you uninstalled all related addons. You may have to install those 3 requested by the skin.
3. If step 1 and 2 fails, back up the skin via Skin settings to preserve the settings and customization you have done to the skin. (You need addon, Skin helper services skin backup to backup your skin). Once you backup up, uninstall the skin and all related addons. Install the skin again and all required addons. Restore skin settings from your backup once you have installed all the addons the skin needs.
4. If all fails, this is not skin related. Something could be wrong with your KODI setup. See if you change to other skins that require the addons (any of the 3) you still get the error.

Thanks for the answer. Yes, I'm using the multimod in one system, but the errors exist also in another system, with the default skin. In the multimod system the textures file exists in the right folder, as it should.
Regarding the addons, all those should be optional,since there are options for them in the skin settings. So they shouldn't throw errors, if they are not installed. In other words the default skin throws all these errors when nothing is chosen by the user.
Regarding the colored studio logos, they show up just fine (when installed). That's what's puzzling me, since they are reported as not found, but show up correctly.