This tool can convert colors between the formats you can see below
$ indicates a hexadecimal input, # indicates a decimal input.
Javascript must be enabled to use this. Tested in Firefox only.

SNES Color$
PC Hex color$
PC Red:#
PC Green:#
PC Blue:#
Convert color the correct (?) way
      

PC Hex color input automatically pads 0s at the end of the input until the length is 6.
So 'F' equals F00000, 0FF equals 0FF000, and so on. You just can't see it.

Format of SNES color: GGGRRRRR 0BBBBBGG (little-endian)
0BBBBBGG GGGRRRRR (big-endian)