Simian Spectrum is one of the three skins released in one part of the Rainbow Smashfest offer. It could be purchased on an individual basis with game coins in late March 2021.
Simian Spectrum could be purchased in the Skins Shop under the 'Rainbow Smashfest' tab for 3300 coins. This skin was available for a limited time and may not be available for purchase in the future.
Details of this skin can vary depending on location, platform or time.