In Sequence, for each enemy, you can see various stats. What does the Spectrum stat mean though? I've posted an example of 2 different enemies.
The Spectrum statistic correlates to the approximate percentage of colored gems a particular enemy will throw at you. It's explained in the tutorial that the color of gems is related to the damage it does. White is base damage, Blue does 2x the damage of White, Green does 3x, Yellow does 5x, and Red does 10x. The base damage seems to vary based on the enemy's Offense stat.
For example, ~60% of the gems the Whompa throws at you are White, compared to the Goldem, where ~90% of the gems are White. The larger blue area in the Spectrum stat on the Whompa means it has a much higher probability of attacking you with Blue gems than the Goldem. The wider the colored sections are, the higher the percentage is that they will throw higher damaging gems at you.