element.style.color will be whatever the stylesheet specifies, rgba(121, 110, 12, 14);, or rgb(... or hsl, #afd544 etc.
How can I convert element.style.color to some standard, comparable value (RGB-triple or hex string for example) using JavaScript?
You can try using window.getComputedStyle(element).getPropertyValue('color').
Should give you the color property in the unified rgb(r, g, b) format.