In both of the rounds 664 and 663, I have placed in the same rank 783. The fact is one of them was Div1 and another one was Div2. Strangely enough, I got almost the same delta change from almost the same initial rating! So this made me think of placing behind 782 reds/orange/purple is the same as placing behind 782 cyan/blue/purple.

UPD: Um_nik gave a really nice explanation for this case (Also thanks to Radewoosh, though I couldn't understand the fact fully from him) . Here is his quote: "Your expected place is not the number of participants with higher rating + 1. The probability of you placing higher than someone calculated as $$$\frac{1}{1-c^{r2-r1}}$$$ where $$$r1$$$ is your rating, $$$r2$$$ is their rating and $$$c$$$ is some constant. Now we sum this (1 — this, actually) over all participants and get the expected number of people who will place higher than you."