need to change bubble colour in scatter plot.

[Swathi]

i have created scatter plot to show qty and cm of current and previous year for all customers

bubble - if(tkt_Year= $(vYear),customer& ' '& $(vYear), if(tkt_Year= $(vpreYear),customer & ' '& $(vpreYear)))

X axis- Sum({<Period,[MonthYear]={ ">=$(=(vMinYearMonth) )<=$(=(vMaxYearMonth) )" }>+ <Period,[MonthYear]={ ">=$(=(vLimitPrevious_Min) )<=$(=(vLimitPrevious_Max) )" }>} [cm])

Y Axis- Sum({<Period,[MonthYear]={ ">=$(=(vMinYearMonth) )<=$(=(vMaxYearMonth) )" }>+ <Period,[MonthYear]={ ">=$(=(vLimitPrevious_Min) )<=$(=(vLimitPrevious_Max) )" }>} qty)

and colur coding for bubble is

if(tkt_Year = $(vYear), Green(), // Green for the current year if(tkt_Year = $(vpreYear), RGB(0, 191, 255) // Blue for the previous year ) )

Now, i need everything should be same and add on for thesese is need to change  bubble colour of current year wherecm2 is less compare with  last year. it should littl echnage of colour , now current year colour is green , if it is leess, it should green+some other or anything to identify the customers by seeing bubble, that customer have less cm2 compare with last year, 

Kindly help ,me to do that little urgent