Hot Rod's a confusing one.
The legs on the original Hot Rod toy were red. The original Rodimus Prime was similarly coloured, though with slightly muted red for the legs, and more orange creeping into the design.
In the cartoon, the two models were blended, and Hot Rod was given orange thighs and black boots, and a red body. Rodimus Prime was given a similar, but darker/less vibrant/matured colour palette.
In the early 2000's Hasbro had lost the trademark to Hot Rod, so all Hot Rod toys were called Rodimus (Animated, Energon, etc)
In 2010, Takara released a combined Hot Rod / Rodimus Prime Masterpiece that had an integrated Hot Rod - Rodimus vehicle mode. This idea was carried forth into the Power of the Primes release.
If you're looking for a decent cartoon Hot Rod, the PotP Rodimus Prime includes a relatively decent Hot Rod inner robot that would probably look decent with the Generations Arcee. The LG45 is a great toy, but a bit more muted in colour which I personally associate more with Rodimus Prime (in terms of cartoon accuracy - I personally prefer the muted look to the vibrant colour scheme), but the brighter TR one which you've gone with is probably closer to what you're after.