Ruddlesden-Popper phase inorganic metal halide perovskites are promising candidates for efficient LEDs with high brightness and color purity. Here, we demonstrate LEDs made from in-situ grown CsPbX3 quasi 2D/3D thin films that are color tuneable across the entire visible spectrum. CsPbX3 nanosheets are used to produce RP phase perovskites using butylammonium as a separating ligand to create BA2Csn-1Pbn(Br/Y)3n+1 2D/3D mixed halide thin films, where Y = Cl or I. The number of CsPbBr3 monolayers in these crystals was optimized by changing the butylammonium concentration. We demonstrate a stable perovskite phase with thin emission linewidths providing points covering the edge of the CIE triangle and a maximum RGB coverage of ~ 130 % of the NTSC color standard. Additionally, we are able to report record efficiencies for blue emit-ting perovskite NCLEDs with a maximum EQE of 2.4 % and 6.2 % at 465 and 487 nm and a maximum luminance of 3340 cd/m2. We also demonstrate efficient green LEDs with a maximum efficiency of 10.1 % EQE, 23.3 cd/A and 9.8 lm/W at 16.3 mA/cm2.