The default theme is all in the app.css file. See the Obsidian CSS guide.
These are the code properties defined, but the colors will vary depending on what language you define for the code block (and between editing and reading modes, as mentioned above). Maybe what you’re looking for?
body {
/* Code */
--code-size: var(--font-smaller);
--code-background: var(--background-primary-alt);
--code-normal: var(--text-muted);
--code-comment: var(--text-faint);
--code-function: var(--color-yellow);
--code-important: var(--color-orange);
--code-keyword: var(--color-pink);
--code-property: var(--color-cyan);
--code-punctuation: var(--text-muted);
--code-string: var(--color-green);
--code-tag: var(--color-red);
--code-value: var(--color-purple);
}