Hey, thanks!! Very helpful. Already made some fixes.

Beepster
Interesting. Might I suggest the theme name "Planet Hoth" when it's done?
 
Totally has the ESB icebase/battle feel to it.
 
:-)

"ESB"? Extra Special Bitters?
 

Hi Craig,
 
I'm with scook on Light Green; I don't think that one can be changed.
 
The color behind the button text on dark blue is under control bar>modules>snap. But then, you probably knew that.

Noticing your Transport Module now time slider (#3374?) has a black border around it. Might look better if it matched the gray BG.
 
"Orange, ProChannel effect header: I want to make this black" - Tungsten theme is black(ish). Can it be extracted from there?
 
Ideally, one color location should affect only one item, but so far Sonar hasn't been coded that way.
I've worked tirelessly with Duckbar's EXE-Color editor to find background, text and slider colors. Some colors only affect one view but some affect more than one view. Some will change items in different views that are unrelated. In X1-3 many view BGs are comprised of graphics and exe color settings (Inspector, Browser & Track view, etc.).
I imagine this is still the case unless Cake addressed these internally.
 
It's a pretty fair bet that all your buttons will be graphic files. Background & text colors are embedded within the sonar.exe file.

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I'm watching this thread since I've also been working on a light theme, though a little different than Craig's.   While I actually prefer the new darker themes with fairly saturated icon colors, it's nice to have an alternative. 
 

The blue button (1/4) next to the word SONAR, is located - control bar / modules.
Scroll right down past modules folders until you see PNG files, the (menu) button is fourth up from the bottom.
Hope this helps.

Please share "Anderton-Light Theme" when you finish this!  it is very nice!

First, thanks to the tips above, which helped a lot. As an update, here's what the step sequencer looks like. Don't hold your breath, it will take me a long time to finish this theme! It actually has a utilitarian purpose - I want to create something super-visible for when I'm doing seminars and workshops, so that even people in the back can see what's happening.