Question

give an example of motion in which speed remains uniform but the velocity changes

Answer 1

Circular motion.

Speed remains the same but velocity changes as the object keeps changing its direction.

Answer 2

"Speed is a scalar quantity" while "velocity is a vector quantity". This means that the speed will only have magnitude while velocity has magnitude and direction as well. So any instance where the magnitude of velocity is considered is equivalent to the speed.  

So to attain a situation or to illustrate example of uniform speed with change in velocity is when the direction of the travel keeps changing. For example, in a circular motion, body changes its direction so velocity changes but speed can be constant.