This blue circle represents a node that has not yet been discovered by the algorithm. The node's name is shown in the center, and its current known shortest distance (e.g., N1.d) is displayed below.
Nodes that are currently in queue are gray.
Solved nodes are green.
Edges look like arrows aiming from starting to end node. Each edge has it's weight c(N1, N2) above.
When algorithm scans edge but does not update distance of end node (N9) it turns orange.
When algorithm scans edge and updates distance of end node (N2) edge turns red.