Need help on building a passive Dim-to-Warm LED array
1) Start by defining your ideal White light.  


For me, it might be 4500'K white 150k lux 40W to simulate bright sunlight   Perhaps you can get this using an array of Philips dimmable 8W PAR30 White bulbs.


2) Then define or simulate the power or lux level and colour spectrum of a sunset using a mix of orange and/or red and dim white and maybe a blue horizon.

3) Then consider a neutral white (4500~5000'K) for your base with the constant sunset lights to warm up the blended light.


Then experiment with dimming the white only to capture the effect of sunset, such that the blue red orange gradients only tint the white warmer.  


This only works well with blended or indirect light sources such as what I tried with ceiling egg grating painted flat black.
It could be perimeter ceiling light with a valence.  If normally illuminate an area with 300W Halogen indirect light (e.g. floor lamp) , consider 25% of this for LED power.  You can get more or less better efficacy, but you are going after special effects.



This was the least technical answer I could make for a non-EE.

  

I modified a Universal Laptop charger with a 4 wire connector and  a few parts with a pot to adjust the voltage 3 to 35V with LED indicator in a small box lower left instead of a fixed 19.5V 65W.  

But I am suggesting "dimmable" PAR (parabolic reflector) Edison-base AC bulbs to match your desire using a Triac control.  Dimmable LED bulbs are pretty common not but none of them match, so I get bulk qty in a box in case of failures.

For the Orange, Red emitters Blue, you might be better off using  RGB remote strings avail on Banggood , Ebay etc.