Hi Andrii and welcome to the forums!
The number is the decimal equivalent of a hexadecimal value that describes the color. If you convert the decimal number '2434847' to a hex value, you get 0x25271F. (The '0x' indicates, that the following number is a hex-value.)
This hex-value 0x25271F describes the color in three bytes, where the first byte (0x25) describes the brightness of the blue color portion, the middle byte (0x27) describes the green color portion's brightness and the last (right) byte (0x1F) is for the red part of the color. Since all bytes don't differ too much from each other and at the same time are quite low (values range from 0x0 to 0xFF), you get a dark grey that might have a
very slight touch of cyan ie. green, (but that might not even be visible).
If you for instance would change the number 0x25271F into 0x2527FF and convert it to decimal, you'd get 2435071, which would color the element bright red.
The easiest way to change the colors would be to set them in "Options -> Preferences -> Appearance -> Theme Editor" though.
-Data