Since you are using Graphviz to do the drawing you need to use the attributes that Graphviz understands. See https://graphviz.gitlab.io/_pages/doc/info/attrs.html
import networkx as nx
from networkx.drawing.nx_agraph import to_agraph
G = nx.Graph()
G.add_node(1,color='red',style='filled',fillcolor='blue',shape='square')
G.add_node(2,color='blue',style='filled')
G.add_edge(1,2,color='green')
G.nodes[2]['shape']='circle'
G.nodes[2]['fillcolor']='red'
A = to_agraph(G)
A.layout()
A.draw('color.png')
print(A.to_string())
Gives
strict graph {
graph [bb="0,0,107.21,46.639"];
node [label="\N"];
1 [color=red,
fillcolor=blue,
height=0.5,
pos="18,28.639",
shape=square,
style=filled,
width=0.5];
2 [color=blue,
fillcolor=red,
height=0.5,
pos="89.21,18",
shape=circle,
style=filled,
width=0.5];
1 -- 2 [color=green,
pos="36.338,25.899 47.053,24.298 60.519,22.286 71.18,20.694"];
}