TIL that these two, John Connor's foster mom Janelle and Private First Class Vasquez, are played by the same person, actor Jenette Goldstein. She is wearing complexion-darkening makeup and dark contact lenses in Aliens.
According to a 2016 interview with her, she was cast because she had the physique the producers were looking for, and also "was a trained actress".
https://toofab.com/2016/04/22/aliens-star-jenette-goldstein-vasquez-titanic-james-cameron-exclusive/