Change a bar's bgcolor transparency based on previous bar's bgcolor transparency

I am working on an indicator, where, based on certain conditions, I change the color of a bar's background (using bgcolor). This is easy to do. But what I now want to do is to edit the bar's bgcolor transparency based on the certain conditions in relation to the previous bar.

As an example, if the RSI is above a certain value, I change the bgcolor to green (this is easy to do). Going further, if the latest bar's RSI > previous bar's RSI and both RSIs are above the threshold value, I would like the latest bar's bgcolor transparency to be 5% less than that of the previous bar. This doesn't apply to just a pair of bars, but to an entire series of bars.

I can't figure out how to do this. Any help?

You can calculate the transparency value into a variable according to your conditions. For example:

//@version=5
indicator("RSI background")

myRSI = ta.rsi(close, 20)

RSIcondition = myRSI >= 60

barAlpha = 100.0

if RSIcondition and not RSIcondition[1]         // first candle to break the RSI value
    barAlpha := 80
else if RSIcondition and myRSI > myRSI[1]       // second candle that break RSI value, and is higher than previous RSI
    barAlpha := barAlpha[1] * 0.95
else if RSIcondition                            // second candle that break RSI value, but is not higher than previous RSI
    barAlpha := barAlpha[1] / 0.95


myColor = RSIcondition ? color.new(color.green, barAlpha) : na
bgcolor(myColor)

This example shows the long way to achieve what you want, but I think it's clearer to understand it that way.

You can also check gradient. It won't give you the full control over the exact transparency of the the color, but it can be more efficient:

gradienColor = RSIcondition ? color.from_gradient(myRSI, 60, 100, color.new(color.green, 80), color.new(color.green, 10)) : na
bgcolor(gradienColor)