Source: Wikipedia
The most significant design is of course their masks. Japanese/Chinese characters depicting elements of the Earth are used, with the exception of 天 (sky) for the Pink Ranger. The rest are 火 - fire (Red), 土 - Earth (Yellow), 水 - Water (Blue), and 木 - Wood (Green).The concept for their robots' design is animals. The basic five are lion (red), ape (yellow), dragon (blue), bear (green) and tortoise (pink).

Pink tortoise that come from the sky? ^^;

Each animal has a shikigami form as well. The gattai has a significant Samurai feel, with Samurai-like helmet, sword and shield. More supporting units are coming up, the three announced right now are red beetle, blue shark (?) and white tiger. The docking concept similar to that of Gekiranger, where part of the add-on always goes to the head, but it's a little more advanced this time, as the ad-ons seems to have their own gattai as well. The beetle, shark and tiger above seems to be able to combine into a bird-like mode.