Hair color is controlled by a handful of genes that regulate eumelanin (dark pigment) and pheomelanin (red-yellow pigment). Dark colors are dominant: black and dark brown outrank brown, which outranks blonde. Red is recessive and needs a copy from both sides — which is why the family redhead question matters. Two black-haired parents can still produce a blonde baby if both carry hidden blonde genes.
发色由少数几个调控真黑素（深色色素）与褐黑素（红黄色素）的基因决定。深色为显性：黑色与深棕高于棕色，棕色高于金色。红色为隐性，需要父母双方各提供一个基因拷贝——所以"家族里有没有红发"这个问题很重要。两位黑发父母如果都携带隐藏的金发基因，仍可能生出金发宝宝。
Frequently Asked Questions
Will a baby's hair color change as they grow?
Very often! Newborn fuzz is not final. Many babies born with light hair darken in the first years as melanin increases, and some blondes turn brunette by age 5.
经常会发生！新生儿的胎发不等于最终发色。许多出生时发色较浅的宝宝在最初几年随黑色素增加而变深，有些金发宝宝 5 岁前会变成棕色。
How does a red-haired baby happen?
Red hair needs two copies of the recessive variant of the MC1R gene. If both parents carry one copy, each child has a 25% chance of red hair even if neither parent is redheaded.
红发需要两份 MC1R 基因的隐性变异拷贝。如果父母双方各携带一份，即使两人都不是红发，每个孩子仍有 25% 的几率是红发。
