there are default gradient colors in qliksense you can use that no need to go for custom colors.
If you want to use gradients other than default you can use color mix function in color expression. You can use qlikview to generate color mix expression. That will work in qliksense too
Are you trying to get a gradient within the bar, so each bar goes from light to dark, or across the bars, so the largest bar is dark and the smallest is light?
In terms of visualisation best practice, setting a gradient within the bar is not a great idea as it might convey a confusing message, and it is also not possible in Qlik Sense. Using colour gradients across bars using the ColorMix wizard is a good technique however.
Depending on the situation there might be other techniques you can look at. What are you trying to achieve or show with the gradient?
Thanks for the reply. I am trying to get gradient across the bars. I am doing a few user studies using colors hence i was trying to achieve Gradient for different colors. I am using this expression to generate a gradient but is not much helpful argb((Sum([Sales Quantity]*[Sales Price])*(255/(aggr(max(sum([Sales Quantity]*[Sales Price]),[Product Group]))))),255,0,0).
Let me see how i can use colormix....