The palette you have is itself very smooth but your histogram has s very small number of bin … that’s why you do not get a smooth result on the plot itself.
Thanks for the answers - However, one more question - How I get rid of the “colored” area where I do not have values? You can see that my values are always below the “diagonal” (ie where also I ve put “COLTEXTZ”) but I would expect that the “upper” part would be filled with white but this is not the case… How can I fix this ?