Android
When you match 3 yellow gems, you receie only 2 mana instead 3.
5 mana instead 6 when mana surge.
Blue gems gives you normal 3 and 6 mana as usual.
It happens all the time.
What banner are you using?
Yes, to expand on what Dorgath is saying:
Some banners actually subtract from a color. If you’re consistently getting -1 to your gem matches, it’s likely you’re using a banner that does that. For reference, the banners that subtract from yellow are:
- Abyssal (Blighted Lands)
- Slayer (Divinion Fields)
- Trident (Merlantis)
- Sorrowful (Sea of Sorrow)
I wrote a tool at http://slypenslyde-labs.glitch.me/gemsofwar/bannertool.html that isn’t quite finished but can help. There’s another guy who has a handy reference chart I haven’t stashed the shortcut for yet.
Hi @Pin
Can you please use the bug reporting template when making a report. Otherwise I’m going to ask you a number of questions which are written there and I look crazy. 
Some of them seem redundant but it’s necessary to help the team reproduce the problem and then resolve it.