Unless I'm mistaken, red diesel fuel is for off-road use only in the U. S. and it's not the same as regular road diesel because of it's higher sulfur content. There is the tax issue of course, but the largest fines I'm aware of will not come from a state, but the U. S. DOT and the EPA. My truck is registered as a farm truck and there's no way I would ever consider putting red fuel in it because of the fines involved. The EPA website has quite a bit of interesting info on this subject. The following two paragraphs are from their website. Of course, it's really none of my business what anybody does, but I would suggest you research this a little further if you're considering throwing some red fuel in your truck.
<From the US EPA Website>
The U. S. Environmental Protection Agency (EPA) is adopting a comprehensive national program to reduce emissions from future nonroad diesel engines by integrating engine and fuel controls as a system to gain the greatest emission reductions. To meet these emission standards, engine manufacturers will produce new engines with advanced emission-control technologies similar to those already expected for highway trucks and buses. Exhaust emissions from these engines will decrease by more than 90 percent. Because the emission-control devices can be damaged by sulfur, we are also adopting a limit to decrease the allowable level of sulfur in nonroad diesel fuel by more than 99 percent.
EPA estimates that affected nonroad diesel engines currently account for about 60 percent of total diesel particulate matter (PM) emissions and about 30 percent of total nitrogen oxides (NOx) emissions from mobile sources nationwide. These proportions can be even higher in some urban areas. The new nonroad diesel emission standards will reduce emissions by more than 90 percent, and are similar to the requirements for engines being implemented for on-road highway trucks and buses.