# On the 4-color theorem for signed graphs

## TL;DR

This paper investigates a generalization of the Four Color Theorem to signed planar graphs, ultimately disproving a conjecture that four colors suffice in this setting.

## Contribution

The paper provides a counterexample to the conjecture that four colors are always enough for signed planar graphs, challenging previous assumptions.

## Key findings

- Disproved the conjecture for signed planar graphs
- Established that four colors are not always sufficient in this context
- Contributed to the understanding of coloring properties in signed graphs

## Abstract

There are several ways to generalize graph coloring to signed graphs. M\'a\v{c}ajov\'a, Raspaud and \v{S}koviera introduced one of them and conjectured that in this setting, for signed planar graphs four colors are always enough, generalising thereby The Four Color Theorem. We disprove the conjecture.