Please consider Pixel Art Premium to be able to create and color artworks without ads.
Pixel Art Premium Subscription allows you to unlock everything, access daily updates and remove ads. Weekly subscription with 3-day free trial period is $7.99, monthly $15.99, and annually $47.99 or equal to the same price tier as Apple App Store Matrix determines as the equivalent of subscription price in USD. Payment will be charged to iTunes Account at confirmation of purchase.
Subscription automatically renews unless auto-renew is turned off at least 24-hours before the end of the current period. Account will be charged for renewal within 24-hours prior to the end of the current period.
Subscriptions may be managed by you and auto-renewal may be turned off by going to iTunes Account Settings. For more information please visit the link https://support.apple.com/en-us/HT202039. No cancellation of the current subscription is allowed during the active subscription period. Unused portion of a free-trial period will be forfeited when a user decides to subscribe.