Creating a command-line interface (CLI) tool that displays syntax-highlighted code requires careful color selection to ensure readability across different terminal themes. The author starts by testing colors from various themes, including macOS Terminal.app, Tango, and Solarized. The analysis reveals that while some themes like Tango offer better visibility than macOS defaults, they still have significant usability issues. For example, certain colors like bright yellow are nearly unreadable in light mode, which poses a challenge for developers who want their tools to work well for a wide audience. Solarized emerges as a standout option due to its thoughtful design. The theme uses a perceptually uniform color space, which maintains consistent contrast across both light and dark modes. It's incredibly popular, with over 15,000 stars on GitHub, indicating a large user base. However, the article highlights a downside: the use of bright colors in applications can lead to display issues, making text appear gray or invisible in Solarized. The author notes that this affects usability, particularly for applications that may not account for the theme's specific color choices. After evaluating these themes, the author presents a final list of acceptable colors for developers. Out of 32 potential color options, only 11 are deemed permissible to ensure readability across common terminal configurations. The emphasis is on practicality for users beyond the developer's personal setup. The appendix adds a personal touch, revealing that the visual style of the article mimics macOS Terminal.app, underscoring the author's attention to detail in presenting this information.