My understanding is the 450 body panel change was a bit of a pain. I understand MB redesigned the quantity and location of the fasteners on the 451 line to make changes easier.
Lots of folks seem to get a second set of the plain black panels and have a local painter redo them in what ever color they want. For some reason hot pink is very popular with British female Smart owners
While in Germany earlier this year, I saw hundreds of variations. In many cities I saw whole fleets for things like pizza delivery. Sort of cool seeing 2 deep by 4 wide parking in front of a pizza house. When a driver came out to leave, he just jumped into the one in front and zoomed off.
Some were awful gawdy (think "max bling" rhinestone studded (yuck)) but many were just too cool to describe... I did not take a camera and the Gvmt cell phone was not equipped with one.... pity too, because I saw some intriguing color combinations and graphics
I think what caught my eye the most were the wheel variations. While the steel stamped wheels have their own minimalist appeal. Most owners obviously had a LOT of cash in wheels and tires. Most of the time with a 3 lug to 5 lug adapter. It appeared to be popular to color match the disk caliper, inner parts of the wheels, and spoilers to the body panels OR tridion color
Curiously most of the tridions were Gloss Black
Edited in...I am sorry I forgot the reason for the post..... Of all the cars I saw and more importantly the one I drove--- interior colors never made any impact on me. I can not tell you what the colors were in the one I drove or any of the very cool Smarts I walked around and drooled over... The interior just did not catch my attention. I think because all the combinations just looked good...red, black, beige/tan interiors all seemed to contrast well in all the cars I paid attention to.
I did like the black leather...but that is just me...I do not like cloth interiors...I like leather no matter what color (well except white too hard to keep clean)