So as stated from the title, it's similar to the Saban Power Rangers shows, but each color has 3 members each. I think it was 2 boys and 1 girl per group or sub group.
For the Megazords, the red one had an eagle, and the purple/black one had a giant beetle or a badly sculpted model of a rhino. The blue sub group was dolphin themed so maybe their Megazord also had a giant dolphin. I only saw like 4 episodes of the show when I was 7 so I cant remember much.
Could it be Chouseishin Gransazer?
Chouseishin Gransazer (Japanese: 超星神グランセイザー, Hepburn: Chōseishin Guranseizā, English: /tʃoʊseɪʃɪn ˈɡrænseɪzər/), translated into English as Ultra Instint Star Gods and the GranSazers or Super Star Gods and the GranSazers or also known as only GranSazers, is a tokusatsu superhero TV series, produced by Toho Company Ltd., and Konami. The series aired on TV Tokyo from October 4, 2003, to September 25, 2004, with a total of 51 half-hour episodes. This series is the first of Toho's "Seishin (Star God)" series.
The premise of this series is similar to both the Super Sentai series and the manga/anime series Saint Seiya: there are 12 heroes, divided into four tribes, and each tribe has a giant transforming robot. The events and characters are described below, using in-universe tone.
Some 400,000,000 years after an advanced human civilization was destroyed by aliens, 12 direct descendants of the civilization's warriors (called "Sazers") have their powers awakened and form four tribes: Flame, Wind, Earth and Water. Each Sazer is based on a Zodiac sign represented in an animal totem or spirit representation. At first, they wage war on each other, but after learning the truth of their ancestry and their reason for awakening, the Gransazer tribes unite to protect Earth from the Warp Monarch, an alliance of various alien species, from once again extinguishing all life on the planet
Found searching for sentai show 15 members dolphin beetle, although it turns out there were 12. :)
