Error in col2rgb(d) : invalid color name in tweenr

I'm getting this error a lot in using tweenr in RStudio on mac but I'm unable to replicate it using dummy dataset. My dataset is a list of data frames with I want to apply tween_states. Works fine on dummy data, but always return Error in col2rgb(d) : invalid color name and recognise my first character column as a 'color' whenever I use real data.