I am having a difficult time getting different sounds out of the Digitone when working on sound design. I would equate it to painting where you always end up with the color brown. Is there any in depth tutorials on sound design? Like an 8 hour class or something?
I’ve been watching YouTube videos, but want to really understand how to use the machine better and to fully understand what settings to adjust and how those effect the sound.
Dave Mech has a paid tutorial on his website.
I don’t know about such tutorial, sorry, but …
on the Digitone you are on a FM synthesizer and I would recommend to spend some time exploring how to create very different FM sounds.
It’s not as direct and IMO easy as using the typical MiniMoog like instrument with subtractive synthesis, but it isn’t witch-craft either. Just a complete different approach. FM is well known for providing the most different timbres with two or more operators.
If you are interested in FM synthesis basics, you could start with this ancient article by Sound On Sound magazine
https://www.soundonsound.com/techniques/introduction-frequency-modulation
You don’t even need to understand the “maths” of this article to get your head around, what concepts lead to which sounds - basically.
The design of the DN takes a lot of this math away and supports direct twiggling of knobs and quite easy success.
Maybe you could describe your “brown sounds” and what you up to achieve?
The slower you go with FM the more interesting and different sounds you can find.
If you go fast (like i did in the beginning), and adjust parameters by difference of 10 or more, all sounds will eventually sound more or less the same, ringing metallic and often unpleasant.
Its happening because all FM parameters depend on each other, and are in a literal sense - linked. so by adjusting value of the second parameter, can exponentially modify how first one behaves. Thus by going too fast you never get the chance for parameters to carry meaningful information, and everything ends up sounding samey.
I believe that if you want theory, the best thing to do is to research FM and not Digitone specifically. Ive never seen a video tutorial on FM that would make it click for me, so i just researched how math behind it works, and it helped a bit.
For practice definitely start with an algorythm with only 2 squares, operator and carrier. Keep MIX parameter so you only hear those two. Try going slow with the values, and go through all available to you sound shaping options, see what effect they have on the simplest FM structure. And dont be afraid to dial things back! Often parameter behaviour can be flipped on its head depending on what other things are doing, so bigger numbers dont always mean louder or brighter.
here are some videos that helped me:
Most relevant part is the beginning, deconstruction of sound wave.
this video has some good explanations of algorythms
However i havent tried Dave’s tutorials, they might work for you better so keep an eye out 
If you have an iPhone/iPad (iPad only it would seem), you can give @mekohler’s excellent Harmonix app a go. It does random patch generation amongst other things. It’s phenomenal for getting starting points for specific patch types.
Also, here is a link with some excellent fundamental information on FM:
Apart from @DaveMech’s courses, I would also recommend @Eaves’s and @substan’s YouTube channels:
Thanks for the mentions !
I have a lot of free content on my channel as well which are actually excerpts taken from the part 1 of the Digitone course (and regular video jams on Digitone).
They are shorts and useful tips that will help you sound design. To dive deeper the course goes deep into how FM works and explains how to approach it on the Digitone step by step plus a bunch of examples on specific sounds to create.
Here’s the first short. You can find all 10 of them on my channel :). Enjoy the exploration of FM! It’s a gift that keeps on giving.
https://youtube.com/shorts/At_XUDYDQOw?si=TFqU0h8X382TLNFi
(By the way The shorts are heavily edited with quick cuts. The pass of the course is much slower and easy to follow. )