http://www.toribash.com/colors.txt


for example

27 amethyst 255 51 242 0

You have the name of the colours and the rgb values of the colours

What's the final digit, though?

Well, there's an optional fourth value for every color, which is referred to as the color's alpha (transparency), so I'd assume it's that.

15 pink 255 51 153 1
16 copper 255 186 38 0
17 skin 242 204 204 1
18 light_orange 255 230 76 1
19 brown 102 51 0 1
20 blood 166 5 36 1
21 juryo 237 191 166 0
22 aurora 245 227 247 0
23 hold 217 71 0 1
24 hold_active 224 133 82 1
25 fracture 128 128 255 1
26 acid 178 255 26 0
27 amethyst 255 51 242 0
28 aqua 0 128 255 0
29 bronze 204 102 51 0

I don't think it's alpha, it looks like any colour that can be equipped is a 0 and any that can't is 1

I still find it kind of odd

The 1 value is used to indicate a color is not available in the shop.