  Visualization linters are end-user facing evaluators that automatically
identify potential chart issues. These spell-checker like systems offer a blend
of interpretability and customization that is not found in other forms of
automated assistance. However, existing linters do not model context and have
primarily targeted users who do not need assistance, resulting in obvious --
even annoying -- advice. We investigate these issues within the domain of color
palette design, which serves as a microcosm of visualization design concerns.
We contribute a GUI-based color palette linter as a design probe that covers
perception, accessibility, context, and other design criteria, and use it to
explore visual explanations, integrated fixes, and user defined linting rules.
Through a formative interview study and theory-driven analysis, we find that
linters can be meaningfully integrated into graphical contexts thereby
addressing many of their core issues. We discuss implications for integrating
linters into visualization tools, developing improved assertion languages, and
supporting end-user tunable advice -- all laying the groundwork for more
effective visualization linters in any context.
