1 INTRODUCTION  
2 THEORETICAL MODEL AND OBSERVATIONAL DATASET  
2.1 Galaxy formation model  
2.2 The Planck Millennium N-body simulation  
2.3 Building a lightcone mock catalogue  
2.4 The PAU Survey  
3 RESULTS  
3.1 Basic results: number counts and redshift distribution  
3.2 Estimating photometric redshifts for the mock   
3.3 Evolution of galaxy colours  
3.4 Sensitivity of galaxy colours to model parameters  
4 CONCLUSIONS