vallejo (panzer aces) actually has creates their colors to be able to paint things without having to mix, or try to color match. they have a set of paints specifically for the splinter camo that encompasses all 4 colors. The base color, i have listed below.
panzer aces- base camuf. splinter 345 splinter camoufl. base
https://www.frontlinehobbies.com.au/products/AV70345its actually more of a gray, then it is a brown. the green splinter lines give a optical illusion that it has a green tint to it.