Interesting topic. I just got back from Kenya/Tanzania/Egypt and there are many large trucks/buses emitting choking black exhaust. Hydrogen is the big hope of the large vehicle, as it is much more energy dense and lighter than current EV battery arrays (unless something changes in battery tech, the weight of batteries creates a large vehicle diminishing return). The question is, as you say, will it be Green, Blue, or Grey. With the demand for renewable electricity, it may take some time for the green hydrogen industry to ramp up. Meanwhile, there is potential for a hydrogen subterfuge (fossil fuel companies perhaps selling grey hydrogen only partially scrubbed of CO2 as blue hydrogen, as a way to keep utilizing dirty natural gas). In any case, the CO2 scrubbing business needs to get much better, while waiting for renewables to grow. Last I heard, people didn't want to invest in CO2 scrubbers as they were afraid it would be stranded tech (superseded). Perhaps it is awaiting government subsidies and mandates. Price? When the dust settles we'll all need to get ready for at least a 50% increase in fuel costs (similar to when the catalytic converter was mandated in the 70s)