It's written that they can be up to 30 cm in size. That means this one might be called big.
It's red back is decorated with dark-red tiny unsharp thorns, the belly side is very smooth and a bit lighter, as it is possible to see at this shot. The creature is so brightly coloured, that your eye hurts, seriously. And it's not a bit slimy or sluggy, as one would expect, not at all.