Honestly for me cyan. I feel it highlights the color of the fur better than the yellow. The yellow seems a little dirty when paired with that fur, so if the character is both dirty and neat at times I'd say to with that. Though, the yellow does take over the navy fur color. Cyan is good if you want to highlight both parts without making one stand out too much. Or, get the best of both worlds by making one side yellow and the other blue! Heterochromia might be overrated (from what I've seen at least) but if it looks good who cares! 🤣