No — the theme only describes the art and story, not the mechanics. Colorful slots on this site come from Pragmatic Play, Wicked Games, Zeusplay, each with its own RTP, volatility, and bonus features, so it's worth checking a game's own stats rather than assuming from the theme alone.
Bubbles by Popiplay has the highest published RTP among colorful slots on this site, at 97%. Not every game in this theme has a published RTP, so this reflects what's actually disclosed, not the full set.