plotting - Need 4D plot (3D + color for function)

I have a function f(x,y,z) of three variables and some constants:

P1 = 630*10^6;
a1 = 6.1;
deltaf = 680*10^-28;
rho = 13600;
Na = 6.03*10^23;
M = 270;
N1 = rho*Na/M;
sigmaf = N1*deltaf;

v1 = 161/(0.7958)^3;
Ef = 3.2*10^-11;
A1 = 3.87*P1/(v1*Ef*sigmaf);

flux1[x_, y_, z_] :=   A1*Cos[\[Pi]*x/a1]*Cos[\[Pi]*y/a1]*Cos[\[Pi]*z/a1]; 

I want to plot this function in 3D frame with color to represent the value of a f(x,y,z) at each triplet point. And need color bar to show variation. Give me suggestions.

I have used the following command but it is not working properly.

ContourPlot3D[
 A1*Cos[\[Pi]*x/a1]*Cos[\[Pi]*y/a1]*Cos[\[Pi]*z/a1], {x, -3, 

  3}, {y, -3, 3}, {z, -3, 3}, 
 ColorFunction -> (ColorData["TemperatureMap"][#3] &)]

I want the plot to look like this:

(It is the last plot on this page.)