Oh, custom color is for 1.11+, sorry. xD
But mixing the colors is still possible, the effect the potion would get mixed with would need to wear of instantly to only have the jump boost be there.
Pastel green can therefore be not possible, but turquoise can be made, would look like pastel green. xD
The item description would also need to be rewritten so the extra effect doesn’t appear:
1.13+ /give @s minecraft:potion{CustomPotionEffects:[{Id:"minecraft:jump_boost",Amplifier:1,Duration:200},{Id:"minecraft:speed",Duration:1}],HideFlags:32,display:{Name:'{"translate":"item.minecraft.splash_potion.effect.leaping","italic":false}',Lore:['{"translate":"effect.minecraft.jump_boost","color":"gray","italic":false,"extra":[" ",{"translate":"potion.potency.1"}]}']}} 1
1.12- /give @p minecraft:potion 1 0 {Potion:{idk how to change the potion effect here},HideFlags:32,display:{Name:"Splash Potion of Illusion: 100",Lore:["I really hope your language is set to English, else this will fail- boost 2"]}}
1.13+: give
s @s
a Splash Potion of Jump Boost 2 (0:10) with a color that is hopefully not green.
1.12-: give
s @p
a Splash Potion of Speech: 100 with no knowledge of how to use translate without JSON text object. (but is still possible with NBTexplorer and plugins)
Didn't want to waste me opening the translation file of 1.8.9
The code for the Name and Lore however should look like this: (1.13+ with 1.8.9 translation keys)
IDK why I can't add the code block into the details?
{display:{Name:'{"translate":"potion.prefix.grenade","italic":false,"extra":[" ",{"translate":"potion.jump.postfix"}]}',Lore:['{translate":"potion.jump","color":"gray","italic":false,"extra":[" ",{"translate":"potion.potency.1"}]}']}}