The logo was changed in 1974 to get more smoother animation. It was nicknamed "The Rainbow HB".
The Swirling Star was introduced in 1979.
In 1988, a new script logo was made.
Hanna-Barbera was absorbed into Warner Bros., though a new script logo (based on the 1961 logo) is being used to promote H-B shows and characters.
To see Hanna-Barbera' on-screen logos and others, see Hanna-Barbera/Other.