I have no idea how tall Blu would be.
If we were to use the actual height of a ROBLOX character...
According to the Roblox Blog, 1 real-life meter is equal to 20 ROBLOX studs, so a stud is 5 centimeters, and a real-life ROBLOXian (that is 5 studs tall) would be 25 centimeters, about 10 inches tall.
...then he'd be very small.
So I'll just say 5'8" instead.