Update – June 21, 2019: Realme has started rolling out ColorOS 6 stable update for the Realme 2 Pro again after it was stopped due to bootloader issues last month. This has the build number RMX1801EX_11_A.21, includes Android security patch for May, 2019 and is 2.68GB in size. It is rolling out gradually, but you can download the update ZIP file from Realme website here and update manually.