User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-6050823-20140222041235/@comment-5043481-20140222121202

Interstingly, the steel uragaan is the colour of tempered steel. If it actually has steel on it, which is possible given its diet of ore, then the colours would correspond to diffentent stages of tempering. The blue on its body scales is a tempering stage used for springs, so it can return to its orgional shape. However, on its back it has yellow. Tools tempered to this colour are very hard.

So his back is hardened to prevent wear when rolling, and his body scales are springy to deflect attacks. I wonder if capcom thought of this?