sigmajs comes with tons of settings, these are passed to sg_settings. Due to the large number of options they are not all listed as arguments, these settings can, however, be found online.
nodes <- sg_make_nodes()
edges <- sg_make_edges(nodes)
sigmajs() %>%
sg_nodes(nodes, id, label, color, size) %>%
sg_edges(edges, id, source, target) %>%
sg_layout() %>%
sg_settings(
drawEdges = FALSE,
hoverFontStyle = "bold", # bold labels on hover
labelColor = "node", # node label color = respective node color
labelSizeRatio = 2,
defaultHoverLabelBGColor = "red", # hover label bg
defaultLabelHoverColor = "white" # hover label text color
)