Each player will need to purchase their own pair of baseball pants.
At the travel level, most teams go with white pants with a red pinstripe down each pant leg. There will be an opportunity to purchase pants during uniform fittings.
At the house level, color is not as important; however you will want your child to have some sort of baseball style pants whether that be white, grey, black, etc.
As teams are formed there will be additional information sent out with links as to what to buy and where to buy depending on the team your child is placed on.