In the summer of 2012 we filed a non-provisional application at the USPTO. We included color drawings (actually, photographs). We also duly filed a petition for the USPTO to accept the color drawings, because, for reasons that presumably have to do with the ability of the PTO to reproduce paper copies of color drawings, 37 CFR 1.84 requires the filing of a petition. It's not a free petition, there's a fee involved.
Now, in the summer of 2015, we received a reply from the Petitions Branch: petition accepted! Oh frabjous day! Callooh! Callay!
Why did it take this long for the USPTO to act on the petition? Only The Shadow knows.
At least in this case, the USPTO actually acted on the petition. We have even older provisional applications in which we filed petitions for color drawings that received no attention from the USPTO. Maybe it's time to ask for the petition fees back, although I'm guessing the USPTO has never heard of interest or compounding.
Please, USPTO, act on these things faster. Three months to act on a petition might be reasonable, but three years? Come on.
And while we're on the topic, in praise of the USPTO, at least it accepts color drawings. WIPO has been dilly-dallying on this for years. Every time I see Matthew Bryan of the WIPO PCT legal division, I ask him when WIPO is going to join the 21st century and allow color figures. Sheesh, they've only been standard in every significant scientific journal since, oh, the 1980's at least. It's kinda hard to meaningfully represent stained cells in black-and-white photographs. The last time I inquired, I was told that there was debate among some countries about the standard to be used. Ahhh.
BTW, it seems to me that to get around WIPO's limitations, one could file an appendix containing a color photo as ASCII text that can be read by an image-reading program. Haven't tried that one myself, but in this day and age it should certainly count as disclosure, at least in countries where they have computers.