Upgrade the skin with Polygonatum sibiricum: players can get Polygonatum sibiricum by opening the portal to decompose skin fragments or the whole skin. Yellow essence can be used to upgrade ordinary skin and make it become a higher level of skin.
Use three skin fragments or the whole skin to synthesize skin: players can get the colorful skin of heroes in this way. There is a certain probability to obtain rare colorful skin when synthesizing.
Generally speaking, players can unlock the colorful skins in League of Legends in the above two ways. For more information, please consult experienced players or visit League of Legends official website.