It has been almost 26 years since we skipped a yellow ranger. In Super Sentai, the last team without is Flashman.
The new team, Juden Sentai Kyoryuger, breaks the tradition thanks to the chief Producer Takahito Ohmori, who had this to say for himself:

“This is actually not the first time a team is without a Yellow member, J.A.K.Q,
Battle Fever J and Dengeki Sentai Changeman never had a Yellow member. When it
was decided that the Kyoryuger’s would be required to defeat a dinosaur in order
to be able to transform, we wanted the characters to be absurdly strong.
In order to show this, we chose to have more male characters over female
characters. Seeing how modern Yellows have been female, we couldn’t have a male
Yellow. If the Yellow was a male, the kids would probably think is feminine and
we wanted to avoid that.”

This has lead to much discussion about the place of women in the series and general sexism in Tokusatsu.

The original post can be found here: http://r25.yahoo.co.jp/fushigi/wxr_detail/?id=20130215-00028313-r25