A small cross is often placed on a child's cot or bedroom wall after he or she has been Christened. The cross takes on various names including: Baby Cross, Christening Cross, Cradle Cross and Infant Cross. The cross may include an image of a cute baby, often in a praying position, with or without angel wings. Alternatively, it may be a chunky toy-like cross in pink or blue, depending of the baby's sex.
It's unlikely a few-weeks-old boy or girl reacts differently to blue or pink - babies know nothing about gender distinction and even less about crosses, baptism or Christening ceremonies. So why do it?
Proponents of infant baptism (perhaps 80% of all Christians) believe that it doesn't really matter whether of not the child understands what is happening. They believe the ceremony replaces the circumcision referred to in the Old Testament as an appropriate initiation into the Christian community. Since we all inherit 'original sin', parents have a duty to their children to baptize them as soon as practicable to receive God's grace. Of course, when the person grows and makes the personal choice whether to sin afresh, then it is that person's responsibility to ask for God's forgiveness. (See The meaning of the cross)
Opponents (including Baptists and Pentecostals) generally do not baptize infants because they believe that a person must desire baptism for it to have any effect. (See Baptismal Cross)