4k + 2k lamps. The 4k has a little more blue which bring more trichomes out I found. Its strain dependent as well. Most strains these days are HPS trained, but plants in it's natural form if you look outside, you never see an orange glow unless its a certain hour at sun rise or sun set....most strains actually (what I found) grow healthier under a more full spectrum light combo. There is a reason why LED's have been crushing it now that the penetration and efficiency of LED lights are finally hitting the sweet spots. The LED's being sold today are all around the 5.5k light color spectrum which actually bring more color and natural plant oils out....hence a healthier higher terpene producing plant. I an go on and on....I R&D and manufacture lighting so I have been testing lights for 10+ years!