DIY LED Light Questions

[Beanz]

Well i was thinking of buying a combination of CREE XR-E G5 Cool White and CREE XR-E Royal Blue how many would i need of each like what is a good amount of each to combine with each other and also what optics should i use? (would using optics enable me to use less LEDs?)
My tank is a 45 gallon tank that is 18" tall(but the water is only about 14 1/2" deep due to the sand depth and stuff), 12" wide and 48" long.

Thanks, Ian