Choosing distinct categorical colors that all work with opposing black gradients

General Usage
1

I’d like to use something like :batlow to choose 3 categorical colors, each to use in a color gradient against black, but some are too dark for enough contrast. How can I simply lighten the first two?

using Plots, Images
pal = palette(:batlow,3)

batlow-eg

g1 = cgrad([:black,pal[1]])

batlow-1

g2 = cgrad([:black,pal[2]])

batlow-2

g3 = cgrad([:black,pal[3]])

batlow-3

2 
using Plots, Images

pal = palette(:batlow,3)
pal_light = pal .+ 0.4*ones(RGB{Float32},3,1)
pal_light = [pal_light[1],pal_light[2],pal[3]]

batlow-light

g1 = cgrad([:black, pal_light[1]])

batlow-1_light

g2 = cgrad([:black, pal_light[2]])

batlow-2_light

g3 = cgrad([:black, pal_light[3]])

batlow-3_light