have you tried to download any of Google's themes and have a look at the files?

RT @sulasno -- I have. So far as I can tell, I have the correct formatting, etc. I downloaded the MacOS Chrome theme and its manifest.json file had no newlines, spaces, or indenting, so I even removed all of those from mine and I still get the invalid manifest error. I added every element in the downloaded theme's manifest.json file so that my json has the exact same number and type of elements but I still get the manifest invalid error.
.
Is there a document/webpage that specifies all possible elements with the appropriate value constraints (for example, the "images" section must be included even if you do not want to use images), and the required json formatting (for example, where there must be commas as line endings), etc.?

take a look here

How to create themes in crx format for Win, Mac & Linux

I even took the manifest.json file that came with the downloaded chrome theme, and modified only the image paths (!) and after packing and attempting install, I no longer get the manifest invalid error, but the images are ignores and none of the color settings are applied.
.
If this is supposed to be straightforward, I'm the most stupid person on earth.
.
btw - I'm using as my model the Brushed theme (not the MacOS Chrome theme). But still, I'd have thought it easy to just create new *.png or *.gif images and substitute the paths, modify the color values and presto-chango I'd have a new look. Absolutely not. Very frustrating even if this is the Linux dev release (I mean, the camo example and Brushed and all the themes on the official site all work).

take a look here

Chrome theme Creator for newest chrome version

sorry I can't be of much help in creating themes in crx

Originally Posted by jstalnak

I even took the manifest.json file that came with the downloaded chrome theme, and modified only the image paths (!) and after packing and attempting install, I no longer get the manifest invalid error, but the images are ignores and none of the color settings are applied.
.
If this is supposed to be straightforward, I'm the most stupid person on earth.
.
btw - I'm using as my model the Brushed theme (not the MacOS Chrome theme). But still, I'd have thought it easy to just create new *.png or *.gif images and substitute the paths, modify the color values and presto-chango I'd have a new look. Absolutely not. Very frustrating even if this is the Linux dev release (I mean, the camo example and Brushed and all the themes on the official site all work).

It's not completely straight forward, I spent hours figuring out the idiosyncrasies. For the current beta 4.0.222.5, colors and tints don't work completely. I ended up using an image for the toolbar, and probably would have needed one for the background tabs, if I didn't let them just take the frame color/tint.

With the image files, I found that Photoshop .png or jpg files don't work unless you save for web. I think this is because photoshop embeds information into regularly saved files (I suspect this is also the case with GIMP). also the img directory MUST be a subdirectory of the theme directory. To use images in any other path will not wok.

This is my manifest.json

Code:

// Created by Daniel Weinstein
{	"version":"1.0","name":"MacGrey",
	"theme":{
		"images":{
		"theme_toolbar":"img/background.png",				
		"theme_toolbar_incognito":"img/background.png"


		},
		"colors":{
			"frame":[168,168,168],
			"frame_inactive":[240,240,240],
			"frame_incognito":[128,128,128],
			"frame_incognito_inactive":[240,240,240],		
			"toolbar":[128,128,128],
			"toolbar_background":[128,128,128],

			"tab_text":[0,0,0],
			"button_background":[220,220,220],
			"control_background":[168,168,168]
			
		},
		"tints" : {
			"frame":[1,0,0.7],
			"frame_inactive":[1,0,0.9],
			"frame_incognito":[1,1,0.2],
			"frame_incognito_inactive":[1,0,0.7],
			"buttons" : [0, 0, 0.1]
		},
		"properties":{
			"ntp_background_alignment":"topleft",
			"ntp_background_repeat":"repeat",
			"ntp_logo_alternate":1
		}	
	}
}

It seems you do need a tool bar image at the mo.
I save my pngs with CS4 and I just use save as?
If your loading your themes with Load unpacked extension you might have to keep increaseing the version number each time you do. I never had to before but when I was trying some stuff before I had to, very annoying. Version 4.0.222.12
And idan where did you get toolbar_background in the colors section, I dont seem to be able to find it here.....
http://src.chromium.org/viewvc/chrom...cc?view=markup
and jstalnak you also might want to look here....
http://code.google.com/chrome/extensions/themes.html
...and the way the file is formatted is json, you can find info on that here....
http://json.org/

or maybe it's because you didn't add a spacebar after the Collen. i needs to be :<space>"

there doesnt need to be a space