The logo was changed in 1974 to get more smoother animation. It was nicknamed "The Rainbow HB".
The Swirling Star was introduced in 1979 and it became no longer in use in 1992.
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. This logo is only used on merchandises.
To see Hanna-Barbera' on-screen logos and others, see Hanna-Barbera/Other.