Something like this would create a 2 triangle plane:
local patch = Model:Create()
local surface = patch:AddSurface()
surface:AddVertex(-0.5,-0.5,0, 0,0,-1)
surface:AddVertex(0.5,-0.5,0, 0,0,-1)
surface:AddVertex(0.5,0.5,0, 0,0,-1)
surface:AddVertex(-0.5,0.5,0, 0,0,-1)
surface:AddTriangle(2,1,0)
surface:AddTriangle(0,3,2)
patch:SetColor(1,1,0)
Then maybe instance more of them and rescale them :
local patch2 = patch:Instance()
patch2:SetScale(2)
patch2:SetColor(1,0,0)