Look for Thomas and Martha on the 1880 census, that is the first census that asks where the mother and father of each person in the household was born.That will help a little with migration pattern of Martha's family.
If you do not have access to the new multi CD set for the 1880 census, there are people on this forum who have their own set.Post a query that will catch their attention "Need 1880 census lookup."
Have you looked at 1850 census index for AR?How many families named Colston are listed?You might look them up and see if one has a dau named Martha about 3 years old.
TX began keeping vital records in 1903, so you can obtain a death certificate for Thomas.It should show the names of his parents.Once you have the name of his father, you can look for that family on the 1850 census, too. Happy Hunting (^_^)