Question: Contour plot with legends and customize color

Dear Users!

I hope everyone is fine here. I have the following functions:

f := cos(t)*sin(x)-sin(x)+(1/2)*sin(x)*t^2-(1/24)*sin(x)*t^4

I want to plot the contour plots with legends like given as (this is the countor plot just for reference):

I want the same coloring to fill the contour plots. Kindly help me to resolve my problem. Thanks in advances

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