This 2003 toilet seat design solves an age-old problem — how to visually identify a still-warm toilet seat so you can avoid absorbing the previous user's residual conducted body heat.
"Being able to identify a public toilet seat that has just been sat upon (and is thus still warm) is of particular concern to a significant number of the population. Without warning, one can easily sit upon a seat and be instantly repulsed by the trace evidence of a previous user. Conversely, if one is looking for intimate contact with an anonymous stranger without the associated awkwardness of verbal discourse, one could seek out the warm toilet seat. The decision to sit or not to sit is facilitated by the colour change of the seat: orange=cool, yellow=hot. The object retains the heat memory of a previous user and displays it as a visual marker for the next user to assess."
I would prefer blue=cool, orange=warm, however.