Or they don't have enough eggs to fill or send extra and they send a few of some other color in the same breed.Or they didnt have the looked for color but figured they might be able to make a sale with what they had. I've offered colors before when asked about birds of a different color because maybe they'll be interested
I purchased some blue columbian brahma eggs and the lady didn't have enough to send extra so she sent some dark brahma eggs along with the Blue columbian ones.