both are suposed to match interior colors exactly, as for dark and light blue not sure, most likely they do have both.
I'd say sem might be a tad cheaper and if you can find an auto body supply store near you, you can get it local.
I use duplicolor and krylon fusion both way cheaper and work great, but color selection sucks.
I also don't mess with TSP, dish soap, or their prep stuff, or even alchol. I buy grease and wax remover from the body shop supply it costs like $8 a quart and will go a long ways. It's what you use to clean the vehicle before paint, and it works great on interiors to remove armor all and any other crap. I can usually get by wiping it off only once, but I I know the part has alot of armor all on it, hand grease/body soil or just looks like it, I'll do it a couple times.
I've done plenty of interior color changes, some complete some partial using this method. I did an entire monte carlo ss everything inside, did my old mans dash cap with sem in his 84, it matches nicely, just finished my wifes caravan went from navy blue to black. I did my 88 k1500 my 86 camaro. The only issues I ever had was cloth seats, had some grey ones and went to black after a month or so of daily driving it faded/rubbed back down to grey, I just hit it again when it got that way.
