dougp:
My sketch folder does not have such a folder within. Are you saying I have to put it there manually?
If you want to install a custom Arduino IDE theme to your sketchbook, yes you need to put it there manually. The theme folder won't be there already, you need to create it.
Or, if you're happy with the default theme of the Arduino IDE, you don't need to do any of that.
dougp:
We *are * talking about the folder with the sketches I've created, the libraries and such, correct?
The sketchbook folder location is shown in the Arduino IDE at File > Preferences > Sketchbook location.
dougp:
So, first off, am I changing the correct values?
No. Since Arduino IDE 1.6.5, some of the theme properties are now set in theme/syntax/default.xml.
dougp:
numeric literals, which had been yellow under the previous dark theme are now black.
That is controlled by the LITERAL_NUMBER_DECIMAL_* properties in default.xml.
dougp:
Likewise [],(), and {}
That is controlled by the SEPARATOR property in default.xml.
dougp:
Specifically, I altered these two color settings with no effect.
# TEXT - LITERALS
constants & datatypes
editor.literal1.style = #006699,plain
p5 built in variables: e.g. mouseX, width, pixels
editor.literal2.style = #F8F53B,plain
editor.variable.style = #F8F53B,plain
In the standard theme file they are: #00979C,plain.
Those theme properties no longer have any effect.
I have attempted to document the Arduino IDE's theme system here:
That repository also contains a dummy library that can be used for testing themes. It can get quite tricky to find colors that provide good contrast against each other for both highlighted and non-highlighted text.