ParametricPlot3D[{{3v Cos[u],3 v Sin[u],1- 3 v Cos[u] -3 v Sin[u]},{3Cos[u],3Sin[u],v*(1-3 Sqrt[2])+(1-v)(1+Sqrt[2] 3)},{3 Cos[u],3 Sin[u],1-3 Cos[u]-3Sin[u]}},{u,0,2Pi},{v,0,1},PlotStyle -> {Red,Yellow,Black},AxesLabel -> {"X","Y","Z"}]