change tanks color from simple to gradient

[Het-005]

Description

Change color of tank ,add some gradient finish which make website more cool.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code

Reviewer: Vinit Shahdeo

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