Ramshorns have color genes that can be turned on and off, similarly to apple snails and why those come in such a ranbow of hues, although for Planorbid ramshorns the combinations are somehat more limited. This one appears to have the brown shell pigment turned off while having brown on the body. If the brown on the body turns off as well, you get a bright red snail (I have a post somewhere where I enumerated how that works with ramshorns and the various colors that are documented...too tired at the moment to remember where that went, sorry - but the point is they can come in different colors).