I will close this one… I did not realise at the time of asking that the RGBs can also be ‘no color’.
So, I changes this :
.customZot-Yellow {
background-color: rgba(255, 204, 0, 0.212) !important;
}
to
.customZot-Yellow {
background-color: rgba(0, 0, 0, 0) !important;
}