The word "firearm" includes pistols, rifles and shotguns in Texas, as well as air guns and BB guns. BB guns are subject to a few unique laws, however. It's not considered an offense to fire one on your own property without intent to injure and these guns must be painted with orange tips.
When people think of Texas, guns tend to come to mind. But contrary to urban legend, the state of Texas has a lot of rules regarding any type of firearm use. In many cases, even the word "firearm" can be expanded to extremely broad definitions, so the laws not only apply to pistols, rifles and shotguns, but they apply to air guns and in some cases to BB guns as well.
TL;DR (Too Long; Didn't Read)
Texas includes BB guns in its firearm laws, although it's not considered an offense to fire one on your own property and these guns must be painted with orange tips.
Air Guns and BB Guns As Firearms
Air guns and BB guns fall under the definition of arms and firearms according to the definitions provided by the Texas State Parks Department. This category includes any sort of weapon by which a projectile is fired due to an explosion created from compressed air or gas or by some mechanical means such as a compressed spring. It's against the law for a person to display or use any device in a Texas state park that falls under the arms and firearms definition unless that person is participating in a hunting activity or they have written authorization to have and use the weapon.
Home Use of BB Guns
It's not considered any sort of offense if someone fires a BB gun within his own home or on private property. Although the force of a BB fired from one of these "weapons" may be enough to break glass or dent drywall, it isn't usually enough to cause actual injury. As long as the person doesn't attempt to cause injury to another or damage property that isn't his, there's no real restriction on using a BB gun on private property.
Marking a BB Gun
A federal restriction that applies in Texas requires that replica or realistic BB guns, often called airsoft guns, must have orange tips that identify them as BB guns. If you're found in possession of a replica BB gun without this orange safety tip, it's considered unsafe because it makes it appear as though you're armed and this can lead to misunderstandings with police. It's also illegal. The state requires that all Airsoft guns have this orange tip when sold or owned.