This color created by mixing water solutions of few ions :
Bluish and greenish tones caused by Copper ions ,
Yellowish tones caused by Iron 2+
Brownish tones by Iron 3+ .
Reddish created by adding iron oxide on top of stain before acrylic protection coat applied .
Cooper solutions should be applied first after cooper is dry iron 2 +
Than iron 3+ , after stain is dry and neutralized iron oxide could be applied on top for reddish tint .
For more gradual transitions the surface can be slightly hand sanded and wiped with acetone solutions .
Despite it is look complicated the process is relatively easy . I was able to finish about 1000 sq. feet for one day and half . Ths concrete slab over 100 year old and has a lot of damages .
On new slab and more attentions to details you can expect even better result.
Stain brand - made by myself . The major components is iron sulphate and cooper sulphate , miriadic acid , soda , iron oxide ( used for fireworks ) . All this chemical available on Internet and inexpensive .
You can do something similar with manufacture made stain but it should be true concrete acid stain not dying stain . Unfortuanately the manufacture made stain is expensive about $60 per gallon , selfmade is about 7-8 times cheaper and more flexibility . The concrete has deep mottled look of natural stone . Unfortunately picture can not show it .
I developed this mehtod by myself and it looks like it outperform all manufacture stain i know both by look and cost . Durability is the same . It is actually upper part of concrete get stained and surface are very durable
In order to develop needs to have some Chemistry background , I have MS in Chemistry .
In order to duplicate and use no Chemistry background is needed the process is very simple .
Mixing different colors plus stensil work and engraving can create very intriguin one of the kind looks for just small fraction of ceramic tiles cost .