Nikos said:
i'll make it no secret, i'm not a fan for colors
so it gives me great pleasure to take on the devil's advocate role here
the obvious counter=argument is, why don't you use icons to tell types apart?
I don't think it's necessary to color lines with different extensions either, but this is what your customers are requesting. You should give it consideration.
I've seen a program from Roxio (Easy CD Creator (version 5.3.5.10) that does use colors for each new music song that is added to the CD burn list. There are a limited number of colors, probably less than 10, but it looks pretty neat. The designers chose pastel colors so they don't become the main focus, just subtle information differentiators.
For reference, here are some pastel colors to look at:
#define COLOR_PASTEL_MAUVE (RGB(0xFA, 0xE1, 0xFF))
#define COLOR_PASTEL_AQUA (RGB(0xE1, 0xFF, 0xFF))
#define COLOR_PASTEL_PALE_GREEN (RGB(0xE9, 0xFF, 0xE1))
#define COLOR_PASTEL_PALE_BLUE (RGB(0xE1, 0xEA, 0xFF))
#define COLOR_PASTEL_PALE_PINK (RGB(0xFF, 0xE1, 0xE4))
#define COLOR_LT_CREAM (RGB(0xFC, 0xFE, 0xE2))
#define COLOR_LT_GREEN_CREAM (RGB(0xEE, 0xF9, 0xE3))
#define COLOR_PEACH_CREAM (RGB(0xF6, 0xE3, 0xA9))
#define COLOR_OFF_WHITE (RGB(0xF2, 0xEC, 0xDF))
#define COLOR_VERY_LT_GRAY (RGB(0xF0, 0xF0, 0xF0))
#define COLOR_WASHED_LT_YELLOW (RGB(0xFF, 0xFF, 0xD8))
#define COLOR_WASHED_LT_PEACH (RGB(0xFB, 0xEF, 0xCF))
My two cents worth