Display color of TTM Wave C in watch list.

Since your question title was so close to the one that covers the A Wave I update your title to show you are requesting a solution using the C Wave. Here is a link to that original post: https://www.hahn-tech.com/ans/ttm-wave-custom-color-watch-list/

Next, I searched the Q&A forum to locate another post where someone requested a scan based on the C Wave changing color: https://www.hahn-tech.com/ans/scan-for-identifying-stocks-with-ttm_wave-c-in-cyan-color-indicating-expansion/

I did that mainly because I am lazy. And the code from post does 99% of what we need for this request. In fact I only need to add a single line of code to convert that to color a custom watchlist column. But I also included that link because in that post we explain very clearly how the color change is determined and what it means for the interpretation of the C Wave.

def cWaveUpper = TTM_Wave().Wave2High;
def cWaveLower = TTM_Wave().Wave2Low;
def cWaveDiff = cWaveUpper - cWaveLower;
def changesToCyan = cWaveDiff > cWaveDiff[1];
plot scan = changesToCyan;
AssignBackgroundColor(if scan then Color.CYAN else Color.BLUE);

Screenshot below shows the result.